There's a law against putting slops back into the barrel, slops being overflow from pints poured, never customers' leftovers. Unhygienic? Pubs were never notorious plague- and death traps, clientele besides. First, I did as much myself, in a pub with a high consumption of the staple beer. Two barrels on the go, can't squeeze slops into a fresh one, can into one that is anything up to halfway down. More than halfway, no go. Of course it needed some common sense and a cellarman who drank the stuff himself. Result, some variety of beer from pub to pub, and a good set of locals would ensure some quality. Now, though, you can't do this. result, more to pay for a pint. In washing the pipes through you have to pull the beer in them through and out. Slops, so to be thrown away, to be paid for somehow. Further to this small-bore pipes are now installed to minimise waste. this hits the quality, passing the beer over more surface area and knocking some of the life out of it, making it tamer, less tasty - less to go up your nose. So, if you want to taste the best it's off to a pub with a taproom. like the Bridge Inn, on the River Clyst, Topsham, Devon... dreams beside, to a place full of beery types.
Maybe breweries are tweaking the balance of beer to allow for this. I have an idea about the current prevalence of bitter over mild. Maybe mild matched the old, fruity pong of horse-filled streets outside. Now the air is laden with the sharper smell of burnt petrol. And don't forget other fragrances, for Friday night used to be bath night, and the average woman up until the sixties owned two pairs of knickers. Oh dear, I'm digressing in a big way.
