Yes a big one and a very good too. They can convince with quality instead of volume.
The thing is, without fake volume some exchanges wouldn't be in the top 20 exchanges and this will be the reason I think.
you're right without fake volume it's hard for what exchange on the top 20 list. but as long as the exchange has good quality and reputation it doesn't matter that he is not in the top rank.
Even Binance might had fake volume in the beginning, unfortunately we live in an age where everything can be faked for profit so i can see how even big exchanges can be tempted.