The design requirements for the rovers (spirit and opportunity) only calls for them to work for months. These rovers weren’t designed to work indefinitely and so they weren’t build as such because if the weight and powerbudget went to a wiper then it is taken away from the science payload; doing science is why they are there in the first place. If the mission is only suppose to last for months, why spend the weight and power on something that only helps with the longevity of the vehicle when it’s operated on the scale of years. Operations with spirit and opportunity for years also shows that you didn’t need wipers for the dust since the Martian winds periodically blew them off anyways.

Edit: curiosity uses RTG for power so it doesn’t have solar panels.