I meant we should care about getting/retaining as much as possible users which means more 'eyeballs' as well (English is not my mother tongue but I translate 'eyeballs' here with people who view content, advertisements, articles about Steem Monsters etc. - tell me if I am wrong) which should lead to more usage as well.

I'm not convinced that people influence people's eyeballs by buying Steem ...

Yes, if someone is buying STEEM that doesn't influence people's eyeballs, but if there are more eyeballs (= more users) there is a bigger chance of more people buying STEEM. Therefore I think the formula more users = more value still should work even on a blockchain based platform.
And that's why we should care about the effect every change has on (potential) new users.