Remember, most of the Tatooine shots were filmed on location in the deserts of Tunesia. So those were all clouds shot in a desert. And the matte paintings of the planet show lots of clouds. The clouds are supposed to be there and are very pervsive. some shots are cloud free, but where I live we have days like that as well. And while I don’t live in what is officially a desert, it is very arid most of our water comes form snowmelt off the mountains. So it would be a huculean task to remove all the clouds. And as someone pointed out, those vaporators need something in the air to pull out and clouds are usually caused by atmospheric humitity. They may seldom, if ever, see rain on Tatooine, but there is moisture and clouds are a natural result of that.

And as a real world example, Mars has clouds.

So clouds on Tatooine is perfectly sound and reasonable.