Tobacco smoke has finer particles than standard glycol-based smoke machines. For concert lighting, tobacco smoke gives a much better effect if all you want to see are the light beams, glycol is a bit coarser and not as smooth-looking in comparison.

You can get a fair bit closer to that look by using an oil-based cracker. Those have finer particles than glycol-based, but they have their own drawbacks as they rely on an air compressor that's either noisy or needs to be placed somewhere far away, and the oil tends to get on every light fixture and surface in the venue. It looks fantastic though.

When they introduced a smoking ban at the concert venue I worked at, I noticed that we had to run our smoke machines a lot harder to get the same looks we previously got "for free" from the punters smoking tobacco.

The reasons against smoking is, smoke.

Doesn't matter were it comes from.

Of course the putting it concentrated in your lungs a far more serious issue than it just being around so your statement stands :)

[edit] No idea where glycol based smoke stands as far as cancer goes