I think some do. If you're going out for the night, then you might well be quite happy to spend £20 on beer and the 'benefits' it brings to your night out. However, if you're going out and can only drink fizzy pop, you'd be a bit annoyed to still find yourself £20 lighter. It's a carrot and...
It would help if other drinks were a bit cheaper. When pubs charge £2 for half a pint of cheap lemonade it's not exactly an incentive. And if you want anything with a bit of flavour such as pineapple juice (for instance) then it'll be more than a pint of ale.