If no reason is given for an up/down vote, you can assume it's for the reason(s) given in the tooltips on the respective arrows.
Question up votes:
This question shows research effort; it is useful and clear
Question down votes:
This question does not show any research effort; it is unclear or not useful
Answer up votes:
This answer is useful
Answer down votes:
This answer is not useful
You can't case a close vote without providing a reason, so that's already covered too.
Regarding the specific question you mentioned...
That one is indeed low quality, and not likely to be useful to future visitors. "It doesn't seem to work" is not an explanation of the problem, it's just a random over-arching statement. It's not clear what the issue is, and the question isn't likely to be useful to future visitors because of that.
So a down/close vote is perfectly reasonable there in my opinion.
To answer your specific question:
Shouldn't we have comment as required input when someone do downvote/close request a question/answer
No, there's no need, that information is already available. Forcing people to comment will just lead to rubbish comments being left, or less people voting because they don't want to have to constantly explain themselves.