Most people when it comes to selecting an exchange to trade on don't take into account the fees associated with each trade that much, simply because most people don't trade enough volume for that figure to have any sort of major significance.
Bittrex was extremely popular. But it's definitely not as popular now, especially after legacy accounts were removed from having the rights to deposit and withdraw without ID verification. That's why you see huge drop offs in volume in Bittrex as of now compared to a year ago.
Thus, it's probably wrong to assume that Bittrex is still that popular as most of these traders who want to remain anonymous are moving towards Binance where a 2BTC threshold is kept for anonymous accounts. For the remaining account holders, though, they're most likely there to trade very specific pairs not offered on other exchanges; or simply diversifying their trading across multiple platforms.
Right! I have seen bittrex to actually lose that recognition since they have decided to shut some people off their accounts without verification and also insisted on still using the old 0.25% trading fees. A lot of traders have moved to the likes of binance which apparently are gaining much more popularity as a result of the fees and that has made binance to be an exchange with the highest trading volume so far.
Bittrex to me right now is still just living in past glories, and with the competition hitting the exchange space gradually, if they do not end up doing much to attract users, they may lose more volume than they already have.
