Because the people who are most valuable to show ads to are also the most likely to be be willing to pay $10/mo to not see ads.

I pay for Spotify and Google Play. If either one of them starts showing me ads, they're gone. It's not me I'm worried about at this point. It's my kids.

Some are likely far over that threshold. However, I doubt everyone willing to pay 10$/month is worth more on average.

Facebook makes $7 per month per user in the US and Canada. So, it's likely fairly close though.

But it doesn't matter if you lose money on those people. The $10/month easily carries all costs even if 0.1% of users pay and the rest gains them zero. (At least, back when I did the math in ~2015, when they were probably a bit smaller than they are now.)

Facebook alone makes $23 per user (from US/Canada) per month so it probably should rather be $50 than $10 per month.

It's per quarter I think.

I believe that was one of the questions Zuck got asked in Congress - why not make paying for FB (and it's subsidiaries) optional in exchange for an ad free, non-data harvesting experience. I get it that many people want the service free and that expense needs to be recouped, but it would be nice to have the option. Perhaps it should even be a legal requirement to have the option.

I think YouTube has something like this (in the US) where you can pay monthly for an ad-free experience?