Originally Posted by Barabaika
I suspect that most children and many women don't know how and why change gears in the derailleur bikes.
Wow. I'm not even gonna touch that.
Originally Posted by Barabaika
I liked the coaster brake when I rode in the childhood, it was very intuitive. I didn't understand why more expensive bikes didn't have it.
Coaster brakes are fine for low speed. Many adults ride in traffic where you need brakes that work at high speeds and can be properly modulated.
Originally Posted by Barabaika
When you commute in the hills, you don't accelerate in the streets going downhill (it's too dangerous), you brake to slow down. So you don't need high-speed gears, and you can adjust the chainring and cog for slower gearing. They don't require ramps and pins, so they're cheap.
Too dangerous to go fast down hills? Eh? That's how you keep up with traffic. I wouldn't ride in DC if I were you. My commute is all hills and if I dragged my brakes down them it would take me forever to get to work and I'd be constantly burning through brake pads. I have absolutely no idea what you mean by the ramps and pins thing.
Originally Posted by Barabaika
A single-speed chain is wide and reliable, also the chainline is perfect. So a commuter should worry less about it. Even if it wears out and wears the cog, this combination will still work.
Modern chains are perfectly reliable. Any worn parts should be replaced,regardless of whether it's a SS or geared setup. As for perfect chainlines,yes,as long as the rear wheel isn't crooked. Remember,geared bikes with vertical dropouts don't worry about chain tension or making sure the rear wheel is on straight.