Not a lot. Most software isn't very parallel. I think 2 fast cores would be the sweet spot for most people, for the foreseeable future.
I think a question like this will get very biased answers, since most people aren't very inclined to post "paid a lot, don't really use it" and rather stay mum.
BTW taken out of context, "people with many CPU cores" would mostly consist of 8-core Android phone owners. They also do little with all those cores.
I regularly see 8 cores over 50% utilization. So sure 90% of the time you don't really need it, but a lot more things are parallel now than you might think.
Consider, if your PC is going to last 3+ years, and you average ~40 hours a week on it then the most demanding 1% is still 48+ hours.
Standard office computer here is a quad core (AMD APU), and it actually makes quite a bunch of stuff faster (e.g. conversion of scanned documents) compared to the previous-generation dual cores.
It was shown that for most games nowadays 2 cores will result in micro-stutter. For example the Pentium G4560 (2x 3.50GHz) has pretty good average FPS, but if you look at the 99th percentile, it's worse than similar priced quad cores.
I think a question like this will get very biased answers, since most people aren't very inclined to post "paid a lot, don't really use it" and rather stay mum.
BTW taken out of context, "people with many CPU cores" would mostly consist of 8-core Android phone owners. They also do little with all those cores.