If we would have more big stakeholders

We do have a lot of big stakeholders. Out of 16 million SP votes on return, only the top 3 votes are over 1 million, and those total about 6 million. The majority of the votes are from a large number of smaller accounts.

Even more to the point, setting aside Steemit Inc, there is probably something like 150 million SP and another 100 million STEEM which could potentially power up. There is an enormous amount of additional stake which could vote, far, far more than return.

In other words, make your proposal more compelling.

the pot will just keep growing without any relevant benefits for us.

There is no inherent benefit from solely from spending money. If stakeholders aren't convinced that the benefits are worth the costs, we are better off not spending it and avoiding even more Steem (whether in the form of STEEM or SBD) flooding the market and driving the price down.

If the proposals are compelling I have no reluctance to support them, but if they aren't, then I'd rather take the benefit in lower inflation.

we don't build kind of an automated 'burn STEEM machine' to at least support the price a bit in the meantime.

I'm all in favor of that in fact that's why I run @burnpost and vote for it. That being said, keeping the funds in the SPS treasury has similar benefit (not being sold on any market), plus a bit more flexibility to fund compelling future proposals, should they be made. For example, at Steemfest a lot of people noted the lack of good proposals for marketing and other community building. I agree and I will look for these proposals to support. But I still won't support them if the proposal itself isn't strong.