Anyone can get followers on social media. But to get on radio or tv, you need connections and money. Also not a lot of people listen to radio or watch tv anymore, especially the younger generation. So if you want to target them, you need to advertise on social media.

I'm not sure how much tracking Twitter does, but in the case of fb and Instagram it's the amount of privacy violating data harvesting they gather and use to target, which has lots of negative uses. That aside, I don't think there's a lot of difference between a fb display ad or tv commercial. If data harvesting and hyper targeting went away I would have much less of an issue with them.