Makes sense, sort of.
It's a similar logic as for when you're mooching around town looking for a restaurant, you'll happily walk into one with plenty of customers, as that's a gauge of quality, but an empty restaurant indicates bad food.

Not sure your critical sociability mass theory applies to big cities, though. Whenever I went into a pub in London I fully expected to meet absolutely no-one I knew. I'm also in two minds as to whether it applies to villages: given a smaller population density, the likelihood of a resident knowing any given client is greater, but could you not argue that the chances of bumping into someone you know in this scenario are virtually certain? Even if people in villages know they're less likely to see their smoker friends down the pub now that the ban has come into force, they're still just as likely to see their non-smoker friends. Arguably more likely.
( .Yeti. El amor en los tiempos del cólera, Thu 22 Sep 2011, 19:42, 1 reply)

True
that could of course be argued, and it does make sense.

However, in that case, what did cause the start of the decline of pubs (the 35 per week on average) at the same time the smoking ban came into place?

The price didn't shoot up, and they became no less attractive overnight for some reason. Short of the ban, I can think of no reason why at the same time as the ban coming in, at least two of the largest chains (the only two I looked up simply because they were the only ones I could think of) had their share price fall drastically - and as yet haven't recovered - and the acceleration of pub closures.
(dchurch bah, Thu 22 Sep 2011, 19:53, closed)