Legislation. If a country requires age verification, identity verification, moderation, etc, it's easy enough to either block that traffic or enforce the local laws. However users can easily circumvent this with a VPN. For some countries, this traffic is still in scope, and so the only real way to prevent it is to block or impose the restrictions on all VPN users.

Could also be spam/abuse prevention. Credential stuffing often goes through VPNs, signup over VPN is a strong signal for future abuse or issues in various ways.

I suspect country level licensing, soundcloud I sometimes seen songs "not available in your country" or something along those lines

It doesn’t really matter if they’re using commercial VPNs or the same upstream providers as commercial VPNs. Blocking an ASN is a million times more effective than blocking single IPs (at the risk of blocking genuine customers). I’ve had customers reach out to me asking to be unbanned after I blocked a few ASNs that had hostile scrapers coming out of them. It’s a tough balance.

VPNs often use providers with excellent peering and networking - the same providers that scrapers would want to use.

AI scrappers made it so much worse. Now most things completely block VPN users who aren't logged in. Reddit and Youtube will refuse to load anything until you log in if you are on a VPN.