There is a reason why a new project can only be listed on a small exchange because the competition to get into the big exchange is very tight.
Usually big exchanges have more complicated criteria to be able to enter a new token in their trade, for example the security of the token because it will affect their reputation.
Also the high cost of paying the listing fee is the reason why many tokens find it difficult to be on big exchanges.
Tokens that are only on small exchanges do not indicate that they are scams but will make them difficult to known and if there is no change they are very likely to end up disappearing

Difficult to transfer when network costs are high like some time ago.
Withdrawal fees? almost all exchanges charge a high withdrawal fee that is why many tokens are useless because they will only give you a loss if you want to sell them