Do you need to wear socks with climbing shoes?

You don't need to wear socks with rock climbing shoes, most people don't, but many people do for different reasons.

If you have blisters, wounds, or want to prevent blisters, a thin pair of socks can help quite a bit with that.
If your shoes are a little bit too loose, socks could help tighten them up.
Some people also just like climbing with socks.

Climbing shoes are generally designed to be very snug around your feet, with no socks in between them and your feet, but in the end it's up to you if to wear socks or not.