Many users bold parts of their questions that don't necessarily IMO need to be bolded.
That's why we have an Edit option. If you feel a question / answer contains excessive bold formatting where it's not needed, you could always edit it out (and optionally request the user to not format the post like that)
This distracts users from looking at the rest of the post, so should I revert this bold to normal text?
Yes. Bold / italics should only be used to emphasize main points. In this case, it's a very short piece of text that is easy to read without a real key point to be drawn. It doesn't need to be in bold.
Why do users feel to emphasize information like this in their questions?
To get more attention perhaps. Some users think their question gets more attention this way. Or it could be an innocent mistake.