Why using capacitor in transformer less ac to dc converter

Question

I saw many transformer-less power supplies using capacitive resistance of a capacitor.

But I don't know exactly what the reasons are for using capacitors instead of normal resistors .

I guess two reasons:

• Capacitors are more isolated than resistors.
• Capacitive resistance waste less power (is it right ?)

Answer 1

Resisters waste lots of power .Capacitors and inducters waste much less power .At 50Hz the inducter would be expensive,Bulky and heavy .Hence the capacitor .