I have found that liquidity is quite poor for many alts even in the major centralized exchanges like Binance or Huobi. Many retail investors who got badly burned have left the market, and remaining investors are much more discerning and don't just throw their money at any hyped up alt. Right now, there are a plethora of DEXes, including those without order books where you can do atomic or trustless swaps, like Uniswap, and they have taken further market share away from the centralized exchanges.

So fudging the numbers by doing wash trading must be business as usual at many exchanges. And why should Binance be immune to propping up appearance? If you don't do anything and the liquidity dries up, all the high volume traders will move to another exchange or leave the crypto market.

I try to use a DEX whenever possible because it is much safer. I may not get the best price but I'm not a high frequency trader so overpaying a little is not a big deal to me.