The issue is people are NOT considerate,
If a smoker is sitting on an outside table, and there are people around you eating, then is it not considerate to not smoke at that particular time? just wait until people have finished eating, or move away if you MUST smoke right at that moment..
I'm not having a go at smokers, it can be ANY inconsiderate action, like letting your kids scream blue murder.. or letting them play on their phones at full volume, in a public place around others.. it's called being considerate..
However until people are more considerate, then unfortunately you will get people that support all sorts of bans.. which personally I feel shouldn't be needed..
BTW the not considerate is not aimed at anyone here, i'm sure everyone here is very considerate.. (judging by the replies anyway!)