Since it's being discussed, here's some reasons I'd top a tree.
1. Line clearance, cheaper than removal and you still get a living although uglier tree. There are thousands of healthy ugly topped trees here.
2. View clearance, someone spends big$ on view property and they should lose it when the trees grow? I wouldn't open up a 360, but a strategically placed window or 2, no problem.
3. Slope stabilization, a big tree has to come out on a slope, top it in increments(eventually to the ground) while the newly planted trees get established.
4. Orchard pruning, more like severe crown reduction. Keep the fruit close to the ground where you can reach it. It's a west coast art form.
5. Take weight/leverage off a rotten trunk, like the cedar picture RBtree posted last week. Pretty tough to replace a tree that big, or even 2/3 a tree that big. I've never done it, but it might fit somewhere down the road.
6. The airport landing zone, we have those here too. Cottonwoods at PDX is a big contract I've heard.
If you call it crown reduction does that make it OK