Well what Ptarmigan said is part of the problem. The real cause in my mind is that breweries on the whole no longer own or operate pubs. They are owned and operated by big companies with no loyalties in the trade, just the profit motive as their raison d'etre.
They buy the beer and spirits from the big breweries/distillers at quantity discounts, and then sell it on to their managers/tenants at a high mark up. These managers also have sales targets which when they meet them, result in the target being raised again.
They can only obtain their supplies from the owners, and they have to pay a lot more than we do in a supermarket, so as a result they have to sell it on at inflated prices.
The pressure for the supermarkets to be stopped selling drink at cheaper prices, comes from these large companies who employ lobbyists, and contribute to party funds as well.
If this chain was broken and publicans were free to buy their supplies where they got the best bargains, then the price of beer etc, would drop like a stone in pubs, and yet the landlords could still make a profit.
When a bag of potatoes needs to be accounted for by producing so many portions, then the accountants are running the pubs,not the landlords, and really the lunatics have taken over the asylum.
Notice I never mentioned the smoking ban, which in my opinion is a red herring [kipper?]