I am a casual rider (~30 km commute as often as possible) in an urban setting.

Reading this SE site to learn about biking (the resource is extraordinary, even though I don't understand every technicality) I see that one of the suggestions given on a regular basis is to have a puncture repair kit.

I ride with a spare inner tube and used a kit maybe 30 years ago - I thought it was an inferior approach to just swapping the inner tube (because you need to find the hole, prepare the kit, glue etc.). I see that I was apparently wrong.

What are the reasons to recommend a kit rather than a spare inner tube?

Is it because

• of the cost? An inner tube for my casual riding is a few euros, I needed maybe one or two last year
• of the reusability? One kit probably serves several punctures but then I would consider having both - in the unlikely case I get a puncture (statistically from past years) I would use the spare, and have the kit in case of a second one.
• of the ecological considerations?
• of the weight? This is a good point but I do not feel the extra tube in my backpack over such a short distance