I think I can understand and see why Binance wants to stay with cryptocurrency trading only. But in the same time I can't but wonder why they forbid buying crypto with Dollar, wouldn't it be better if they allowed people to buy crypto with Dollar? They would expend their user base, or am I missing some information here?
Also its kinda funny to see how much even wrong rumors can affect crypto prices.

the question is "do people really want to buy altcoins with fiat"?
adding a fiat market is not something easy like adding a new altcoin to your platform! it will bring banks and all the fiat headaches such as KYC/AML and the regulations that come with it. and for what? will users really use these fiat markets? i doubt it. take a look at the fiat volumes of altcions, the bigger ones may have some volume but it is not bigger than the same volume in same_alt/btc market and in general fiat volume doesn't exist for the rest of the altcoins.
so it is only logical that they don't want to add it.