Why doesn't every ecosystem just do the aggregator pattern?

(Ignoring the fact for a moment that I think the aggregator pattern is often less beneficial for society overall.)

The reason is because it's impossible to become an aggregator from a standstill.

You can't simply create a platform and have the aggregator pattern develop.

You first need significant, even dominant, consumer activity in that category, which you can then develop into an aggregator by bending the incentives of content producers.

You need to get the lines of gravity to loop back into yourself and get the aggregator flywheel going.

This requires a mass that stands out prominently from everything else around it.

A proto-aggregator will also have significantly worse potential of downside risk for marginal creators, so if they have no short-term benefit to offer creators, they will never get going.

If you already have massive consumer engagement that is significantly beyond competitors, you can parlay it into becoming an aggregator.

But if you don't, your best choice is to open up your ecosystem to make it clear that you can't become an aggregator, so you have an edge over other similarly nascent ecosystems.