Why not reduce alcohol tax in pubs?

I've long wondered, but not known where to address the question, why the UK doesn't seriously reduce the tax on alcohol in pubs and seriously increase the tax on alcohol in supermarkets?

It seems to me that it surely, surely must be healthier for people to be drinking pints in their local pub than alone at home. It would also increase the custom and footfall in pubs which we all know is a struggling industry.

Equally, it cannot be healthy that people are buying 4 cans of Tesco lager for £1 or £3 bottles of wine and drinking them alone at home.