I dont… its just expensive… do you? if so, why?
Yes, because it is profitable
Currently my largest aircraft is a 737-900ER on a 7000km route. I do not use 1st class at all, as I found it to not be worth it on smaller aircraft. However, I think when I start with the larger aircraft on longer routes I will add a first class to these!
I use first class even on an EMB190 ... however, it depends on the market. in the US there is a good first class demand even on domestic routes.