Keyboards, speakers and cell phones don't impose on others if you aren't disrespectful to people around you.
I'll be using a quiet keyboard (crappy or otherwise) if I end up in an office environment. Loud keyboards are a hobby, hobbies stay at home.
Cell phone...don't have one, but when I get one (more of an if actually, I don't want to be contacted if I'm out of the house) I won't be one of those pricks who makes/takes calls in situations where either my attention to the call would be rude to the people I'm with or the presence of my voice could be an irritation (on the bus, in line at a check out, etc)
You're stuck in the headphones = portable mindset. A $200 pair of headphones can sound better than speakers costing $1000+ dollars, so if you want to listen to music at home on quality equipment and don't have the budget for expensive speakers you can get more bang for your buck buying a decent pair of headphones.
Alright, if we're talking about exclusively for home use (or studio or similar) then you've completely got a point.
For portable use though, surely you agree open are unfit?