I agree. I think people have been drawn to smaller exchanges in the past due to lack of options. For example, during a bounty distribution a token might be listed only at the smaller exchanges, forcing the bounty hunters to register to these exchanges to liquidate their bounties. These exchanges also offered tokens that the bigger exchanges were more reluctant to list. Now, as the market has matured, we have a better idea of who the winners and losers will be in the long run, and in large part the winners are listed on the big exchanges. So yes, it's best for investors to stick with large, reputable exchanges.
To further put a voice to why people would still choose smaller exchanges against established and bigger once, is nothing but the reason of fund.
An ICO sometimes genuinely has a target for a bigger exchange like binance for instance and they publish it in their white paper, some of the names they would subscribe to in terms of exchange but if adequate funds are not raised at the end, they opt for smaller and new exchanges.