This year I contacted three, heard back from two and got admitted to those two programs which were my only two applications. I'm in bio and I can't imagine deciding on a school without getting a really strong feel for the PI I'd be working for and their lab group. If you won't work well with someone your PhD is going to be a nightmare. For both PIs I extensively emailed back and forth, had a phone conversation and then talked with them extensively at the prospective student weekend (outside the scheduled interview time). I do agree that you shouldn't be asking questions you can find on the school's/department's website, but you should find out the PI's advising style, how on track their students are with their research, what funding they have for project's you're interested in, etc.