I climb only to fall,
and people often avoid me.
They may not care at all,
but they all know that they need me.
I can fill the streets and invade your house,
but most of the time I fall under.
Leave you feeling unaroused,
and even make you wonder.
Who or What am I?
I'm thinking water
I climb only to fall
Evaporate, and fall as rain
and people often avoid me
Not in my case, I love when rain hits my face
They may not care at all, but they all know that they need me.
We take it for granted sometimes
I can fill the streets and invade your house, but most of the time I fall under.
That's what rain does, but mostly it gets drained
Leave you feeling unaroused, and even make you wonder.
Sadness and contemplation
The rain.
Explanation is pretty straightforward.
I climb only to fall, and people often avoid me.
Water evaporates and gets into the clouds only to come back down as rain.
They may not care at all, but they all know that they need me.
You don't really think about water's circuit, but you need the rain for crops and chill outs.
I can fill the streets and invade your house, but most of the time I fall under.
Heavy raining can cause flooding, but normally it just gets into the ground.
Leave you feeling unaroused, and even make you wonder.
Unaroused as in "not wet"? :) Make you wonder - rain makes us melancholic.
You are
Fire
I climb only to fall,
Fire flames "dance" up and down (climbing and falling constantly)
and people often avoid me.
They do in order not to get burned
They may not care at all,
It is abundant
but they all know that they need me.
Fire is indeed very important thing for human beings
I can fill the streets and invade your house,
A great fire can do this. Such an "invasion" would be pretty devastating.
but most of the time I fall under.
Most of the time fire is placed under the thing you want to heat up.
Leave you feeling unaroused,
When your inner fire leaves you, you become "unaroused"
and even make you wonder.
People often stare at the flames and wonder...
Are you
Sun?
I climb only to fall,
Sun climbs to its zenith, then falls to horizon.
and people often avoid me.
People try to escape sunburn or wear sunglasses.
They may not care at all,
People usually don't think about nature of Sun.
but they all know that they need me.
Without the Sun Earth would be a cold empty planet.
I can fill the streets and invade your house,
Sunlight may pass behind closed doors and windows.
but most of the time I fall under.
Daytime is not always long, and houses often hide sun before the actual sunset.
Leave you feeling unaroused,
May mean cloudy and gloomy days, when sun actually gives light but cannot break through skies.
and even make you wonder.
May refer to beautiful sunsets and sunrises.
You are
Water.
I know this answer has already been given, but giving some different and hopefully more complete reasoning here.
To the lonely I call (the title)
People often suicide by drowning themselves and/or jumping off bridges into water.
I climb only to fall,
The water cycle; evaporating into the clouds, only to fall as rain - and continue falling by running downhill.
and people often avoid me.
People generally avoid puddles, avoid going out in rain, and go around lakes and ponds or over rivers and streams - not through them.
They may not care at all, but they all know that they need me.
Many people aren't particularly concerned about their water intake, but we all know we need water to live.
I can fill the streets and invade your house,
Flooding does these, of course.
but most of the time I fall under.
Typically, rainwater falls under streets through storm drains, and wastewater falls underground and under streets through sewer systems; fresh water comes to our homes etc. through underground pipes, and more generally, natural water is below ground in aquifers.
Leave you feeling unaroused,
Cold showers!
and even make you wonder.
Rainbows!
Those last two, which I don't think anyone alluded to, inspired this answer.
You could be
Summer
I climb only to fall,
Summer is only present before fall (autumn) comes in
and people often avoid me.
People like to avoid extensive heat in summer (i.e. by using air conditioning) (thanks to mr23ceec)
They may not care at all,
Some people are neutral to summer
but they all know that they need me.
Season cycle is necessary for earth to provide the plants etc. Summer is crucial to the crops etc.
I can fill the streets and invade your house,
Summer fills the streets and your house with hot air
but most of the time I fall under.
3/4 of the year it waits to come back
Leave you feeling unaroused, and even make you wonder.
High temperatures make people more lazy and "unaroused" and thinking of not really important things and "wonder"
I'm surprised no one suggested:
The moon
I climb only to fall,
Rising and setting
and people often avoid me.
Going out at night
They may not care at all,
Night-people
but they all know that they need me.
Seeing at night?
I can fill the streets and invade your house,
Light from the moon
but most of the time I fall under.
more so in the summer
Leave you feeling unaroused,
I'll bet the moon is a god of virility/randy-ness or something somewhere
and even make you wonder.
"What's out there?"
Could you be
Alcohol
To the lonely I call
Stereotypically people drunk after a break up or when lonely
I climb only to fall
Alcohol is produced through an exothermic reaction, which means it gains a lot of energy, and then lets it all out.
And people often avoid me.
People avoid alcohol as they believe it is bad (it kinda is)
They may not care at all
Some people drink a lot and don't care for their health in doing so
but they all know that they need me
Maybe a stretch bu alcohol is a great sanitiser and can keep you from getting bacteria in your body
I can fill the streets and invade your house
Drunk people on the street, bottles in the street, bard lining streets and also people drinking at home
but most of the time I fall under
Alcohol makes people throw up, which typically will fall under their feet
Leave you feeling unaroused, and even make you wonder
Drinking often makes people tired, and also can make people say very strange things - or making them wonder strange things
