You are right about the countability. But you are not right to expect any logic in English. Sometimes there is some, and sometimes there isn't. There are rarely reasons for it.

I'm a native English speaker with a B.A. in English and I don't know. I don't even know if you're question is correct or not. Perhaps if you give examples of sentences causing you confusion I could help.

@Anna Lemon-Gray Thank you :D

I don't know why, but my memory tells me it's a countable and sometimes logic says that it is not countable. What do I mean by non-countable? For example, the history of headache (not, headacheS) OR the glory of headache (not headacheS) or , "oh, the pain of headache for us, humans!".

@John Thank you so much!! :D:D