I have a kickstand on my commuter, but not on my tourer.

I find a kickstand useful for quickly parking, to get stuff out of my bag on route, while opening doors to bring bike inside etc.

Fully loaded touring bike is much more prone to toppling over, so it gets leaned or lain (what a funny turn of phrase, is that english?). Double footed kickstands are more stable and probably less likely to damage the frame though when loaded.

I think it's mostly a matter of habit. If I didn't have a kickstand, I'd probably quickly get into the habit of leaning the bike instead.

If you haven't got a kickstand plate braze on, be careful not to tighten the bracket too hard as this may damage the stays. May damage the paint as well.

They are quite heavy as well, if that's an issue for you...