You don't have to. Consider however that Paleo age people didn't have access to round the clock food sources so chances are they weren't eating 3 meals a day with unlimited snack potential. By fasting you are giving your body a chance to clean itself up.
Intermittent fasting is wonderful to do for overall health purposes! It helps further balance your hunger hormones and increases growth hormone for faster muscle repair between workouts. It burns more body fat and sends your body into ketosis. It optimizes brain function and reduces inflammation. Moreover, it has been founded to help the body ward off disease and live longer!
Fasting is a nice by-product of Paleo. You do not have to fast, but you can. The first time I skipped breakfast and lunch (unintentionally) without getting hungry or onery, I was amazed.
I routinely skip breakfast (i'm just not hungry). And eat lunch, a snack/protein shake, and dinner between 11am - 19pm. That's just what works for me. I turn into a 16/8 IF (fast for 16 hours, eat within an 8 hour window) without trying.
When I was SAD, I could not go 4 hours without having a blood-sugar crash.
IF if and when it works for your lifestyle.