It is simple, all the trading pairs are not available on major exchanges. This means not just bounty hunters alone need to trade at lots of exchanges but traders who carefully choosing trading pairs might get enforced to trade in multiple exchanges regularly.

For example, lisk is not available on many exchanges whereas it has good community and good reputation among crypto adopters.

I will recommend anyone to trade in bittrex as it is my favorite crypto exchange. I needed to submit my mobile number and ID proof to clear their KYC before continuing with them yet it is good to have bigger withdraw limit on daily basis.