Other than be happy for that attention and being curious of what extra things you can find in their field, they get quoted and that pushes their reputation a little higher. Locking up works heavily limits that, and the only reason behind that is a promise of a basic quality control when accepting works - and it's not ideal, there are many shady publications. Other than that it's cash from simple consumers, subscriptions money from institutes for works these company took a hold of and maybe don't have physical editions anymore just because, return to fig. 1, they depend on being published and quoted.