Regulatory capture through a higher barrier to entry. Any social media platform that wants to compete with Meta's portfolio will now also need to have an age-verification system in place (which is guaranteed to introduce higher costs). Meta can likely afford to eat the costs here as a tradeoff for the higher impact on smaller players.

It also gives them more information on users as a bonus. Further, verification with a real ID is also a quite effective barrier against excessive bots.

I would think the barrier to entry gets lower because Apple/Alphabet handle age verification, and they let apps/websites use that verification.