Binance is trying to work at the market making aspect to offer people volume and liquidity, which they do a reasonable job at, but it's not a DEX. It's still Binance in full control over the development and whatnot. If they choose to stop being a market maker, the volumes will collapse and their "DEX" will be left empty.
Volume, liquidity, tight spreads, that's where all DEX's struggle with. It takes years to grow organically, but who's going to wait years?
I am agreed to you with this point that if have not more volume people will not use it. Really jot only decentralised exchange even if centralised exchange also lack of volume and liquidity people obviously avoid that exchanges.