Nobody is draining the DHF. All of the funding to the stabilizer is being sent back to DHF (generally within an hour) along with something like $20K USD per day in added profit. The funding inside the DHF is increasing every day at a furious rate. That's hardly "draining".

Similarly, post rewards get sent back and serve as more future funding in the DHF.

That also answers this question by the way:

So if nearly all funding is getting dumped on the market, what's the difference between projects that are adding features to the ecosystem and @hbdstabilizer?

The other proposals don't return all their funding with an enormous profit to the DHF. They may do some good for Hive, in fact I'd say most if not all do, but it isn't a 40000% (approximately) ROI.

The reason these proposals get funded so easily and consistently is that they have large negative cost (i.e. profit) and Hive stakeholders, on the whole, aren't dumb.