There are a few differences. For one, it's much easier to regulate the sale of alcohol and tobacco, the level of friction is much higher and usually involves an in-person interaction with an adult. Visiting some dodgy website or downloading a VPN is much easier.

Second, the peer pressure to drink/smoke has never been as strong as the network effect of social media. Almost all 15-year-olds are on some form of social media, I don't think you can reasonably expect they will suddenly stop wanting to socialise outside school. Their entire identities are built around their online presence; that was never the case with smoking or drinking, at least not on this scale.

I'm sure it will have some effect, but kids are clever, and they have lots of time, they will find ways to bypass these fairly weak bans. Imo, the only way to do this is to provide an alternative along with the ban, like what the Russians are doing with Max as a replacement for Telegram/WhatsApp, though that's not entirely successful either.