In these both exchanges have huge users all of the world, so they generate so much trading volume,if any coin listed in their exchange, those coins price rocket speed increase, thats the reason so many newly lauched coins wants to be listed in these exchange,I think it is one of the major reasons why if there is any cryptocurrency that wants to be listed in coinbase, the price will automatically skyrocket. The same thing goes with binance.
These exchanges always listed true and trusted platforms coins, thats the reason investors buys these exchanges coins blindly.