Local councils are funded with tax payer money yes. The establishment in which you buy drinks is not funded (entirely) by tax money and by purchasing a drink the use of the facilities, lightning, heating, space AND toilets is factored in.
In reality what you are asking is that your tax money is used to create/fund toilets (naturally close to areas of drinking where most pissing takes place). Except of course that you have already paid for the use of a toilet when you bought a drink. So really you want to pay for two toilets and basically use one. Why? so when you drink too much you don't need to think about peeing before you go...a basic function that many children have mastered.
Bars, pubs and restaurants, I'm told, have toilets. Why do we need more? -Let's not forget why most public toilets closed to begin with, besides cost. Drugs, rape, basic disgusting and intentional misuse, that sorta thing.
In my opinion the government and local councils got this one right.
Forgive me if I assume that you're an adult; with the ability to gauge how much you've been drinking against the amount of time you can be away from a toilet.