The advantage I see with using different projects for different purposes is that it is hard for one token to be all things for all people, especially if you don't have a well funded full time development and marketing staff!
I am hoping that SMTs will solve this problem for Steem for content needs, as they can be configured in multiple ways. When it comes to various use cases, there is space for many, many tokens and chains, though some will be more utilized than others. I see it kind of like audience tickets for events. Some might have mass appeal like NFL, others are like the ballet. all can have value as long as there are buyers of tickets.