I guess in older times even dying long after breeding could have had an effect: not being able to look after children => less chance of survival of children carrying same gene.

You are right that in modern society this effect is not so powerful probably, but if we take this reasoning forward, it could mean that diseases of old age will be more and more prevalent as there is no selection pressure for defense against them. Is this happening already?

> Except people rarely die before breeding age from smoking (ever?), so no effect.

Grandparents provide some survival and family size benefits.

with the stigma placed on smoking in many societies smoking could in fact inhibit ones ability to breed (or at least influence it).