There are plenty of ads on Twitter and thus plenty of advertisers. The problem from Twitters point of view is partially that those advertisers don't pay enough,

There are plenty of ads on Twitter and thus plenty of advertisers. The problem from Twitters point of view is partially that those advertisers don't pay enough, and more importantly that in many cases they aren't the sort of company Twitter wants to be associated with. Even ignoring the money, Twitter would much rather have Disney as an advertiser than 1000 different drop shippers.