Yes @alhoppo that is true, sponsors can help, but it doesn't matter it all about numbers.
We could then also compare 200.000 youtube subs to 200.000 on Steemit, and guess what would happen then to a sponsor? with people that actually interact, they would love that even more.
Also, sponsors are not always keen on working with people on youtube I've only ever found 1 that had reasonable terms. But I mean sure, for some niches it really works and they earn a lot of money with sponsoring. Yet most it's just referral links and if people don't click it?
Also notice I'm getting an average of 1300 views on my videos in the first 7 days, maybe 2600 in the first month, that is not super attractive to sponsors either.
But in all fairness you make a good point, sponsor income shouldn't be neglected :)