Can someone explain to me why so many flip-flops are being made with ridges and bumps?

I went from shoe store to shoe store, looking for some flip flops to wear this summer for the beach. Either they were leather, which is awful when wet. Or they where plastic. I didn’t mind the plastic ones but they all had ridges and bumps that irritate my feet.

Another thing was that many of them have the front a slight degree higher than the heel part, and the heal part slightly leans downward to the right for the right foot and the left side for the left foot. My daughter didn’t believe me till she tried them on. It feels weird. You can also tell by laying the shoe on a flat surface. So why are shoe manufactures trying to make their shoes uncomfortable? Oh, I forgot to mention, this was only on womens shoes. I finally had to buy my flip flop from the mens shoes. They were even without all that bumpy crap and didn’t leave me feeling I was standing in sand.