By TV, you mean trading volume right? I don't think that's surprising considering how many aggregators or websites like Coingecko use that metric to show how reliable the exchanges are. Higher trading volume means higher liquidity, so anyone can trade without fear that their order will significantly affect the market. Let's say you want to sell 10 BTC, you'd like to sell it on an exchange that can handle such volume without affecting BTC price too much or you will lose some profits from selling them. You need to see their liquidity to find an exchange that can do that, which probably means looking at their volume, order book depth, etc.
Obviously you should not put all your focus on trading volume, but for exchange it is a simple marketing strategy that works and quite cost-effective so they keep doing that. CMIIW.