Because exchanges have only one aim: Making money from the traders by collecting fees.

Most exchanges don't want to get involved in politics.

Binance did it by removing BSV but they still keep BABABC. BSV was way over the top I guess. Bcash is not much different but Roger is keeping the heat just enough (to not  make the chicken all burnt out) so he doesn't get kicked too.

It is very clear binance don't like bcash but they still keep it. It is Because there are people who trade bcash and binance makes money from those trades. It is a though decision for them.

And if you are a newly established exchange, way way smaller than binance, you don't even have a choice, you have to add whatever which makes you money. Ripple, bcash... even bitconnect (remember thise days people were trading that shit on the major exchanges  even though everybody knew that it was a scam)