Why is it bad to live in plain areas?

There tends to be less Natural Resources to live of off. Or they could be harder to get.

Plain areas always due to topographical similarity lack the ability to retain water. Underground water resources are the only effective way of availing water during summer.Moreover during heavy rains the stagnant water could cause problems for transportation and hygiene. Cultivation could be a problem in such areas as the ground could be dry due to lower water retaining capacity and lack of availability of water is a point worth mentioning.