I've used to study about uniform spaces from the book of J. R. Isbell named simply "Uniform Spaces". Isbell defines them using something called uniform covers (confusingly calling them uniformities), which is intuitive for me, and I prefer it over entourages of Bourbaki.
The study of uniform spaces by itself, to study them just to study them, seems interesting, and a nice way to pass time for me. However, in all this time spent on them, I'm unable to find a real reason for why the field is important in any way. The objects in it seem too abstract, it seems to me that anything useful would be covered in the theory of metric/metrizable spaces already, and there really is no need for something like uniform space. Moreover, the theory of uniform spaces doesn't seem useful for theories of metric or metrizable spaces.
It seems to me that uniform spaces are just a curiosity of mathematics that doesn't really have any applications. If anyone knows of any convincing (or less convincing) arguments for why to study uniform spaces in the first place, I'd be glad to hear them.
I saw other questions like this but I still don't see any appeal in uniform spaces other than being an interesting theory.