Why is it "taking a picture" and not "taking pictures"? I wouldn't like to have a camera for a single picture only. :-)
I agree with you. I had a camera that broke after the first shot and I got really upset.
Maybe you should report it next time. In fact, I would suggest “A camera is a tool for photographing”, which IMO covers all bases.
Because countable nouns in English nearly always need some kind of determiner in the singular - an article such as "a" or "the", a possessive adjective such as "my", a word such as "many" or "all", etc.
Cameras are countable. Indefinite, singular countable nouns are preceded with "a" or "an". If you just say "Camera", it sounds like the name of someone or something specific.
I know its so annoying and to strict for a whole sentence to be wrong, very de motivating for me