This isn't at all surprising given the high volume on Binance, there's just more scope for profitability. Couple that with an attractive fee structure compared to some competitors.
For daily or regular traders fees is very important and if this is the minimum as compared to the other exchanges then daily add up a good amount at the end of the month . So today we have so many people who are doing this full time and some credit goes to binance which is making it possible .
It's something that is oftentimes overlooked. I noticed it myself quickly in my earlier days of trading. When trading small margin in high liquidity margins I would sometimes have a daily trade volume of 20 times or more my entire balance. That was on bittrex which meant I was paying 0.25% of that 20 times which came out to be 5% per day. When transitioning to binance this was instantly lowered to 2% and even lower if using BNB for fees. That 3% a day really adds up over time.