Because people are different, and so are pubs. They come in all shapes and sizes - big pubs, small pubs, posh pubs, basic pubs, gastropubs, basic food pubs, Sky Sports pubs, summer pubs, winter pubs, pubs that welcome children, pubs that don't, quiet pubs, pubs with music, pubs without.
The Great British Pub is a much loved institution, envied by people from other countries who love using them when they visit the UK. It's bad news that so many are closing: once they have gone they've gone, and it's hard to see them re-opening. That would be a sad loss.