If you asked me 10 years ago, does a photographer need to carry liability insurance, I would have probably looked at you crazy. Why? At that time, I knew of nobody that had been injured or killed while taking a photograph. I would have told another photographer, "Just cover your gear and you're good!" Today with photographers taking photographs on more and more railroad tracks (usually illegal), private property, and other places; placing clients in danger, I have done a total about face on this subject.
One of the first weddings I've ever shot, I ended up booking, because the other photographers did not carry liability insurance. The venue required only $100,000 at the time, and I was covered for that. I didn't think anything of it though, until after the fact when I found out why I had won the booking, and started seeing more and more venues require liability coverage. These days, usually between $1 Million and $5 Million at some of the premium venues.
Simply put, EVERY vendor you work with should be insured for the unforeseen. In most cases, the insurance is pretty affordable, and there are companies who specialize in photography studios and businesses. This is a legitimate question to ask your photographer, and the answer should always be, "YES!"
If you find a vendor who DOESN'T carry basic business liability insurance, be very concerned. This could be a signal that he doesn't have the other requisites in running a legitimate business in his state or city. Hope for the best, prepare for the worst.