This is something that happened to me quite some times. I have been trying to be polite about it, but most people simply don't care, so I'm throwing politeness out of the window.
You see, the day after I upload a picture, I check my account to see its reception, mostly the comments. And while I'm usually satisfied with the comments my pictures get, there are many times in which I find stuff like this in the comment section of a pic:
"Hey, do you do requests?"
"Can I have a request?"
"I have a request!"
And so on.
Seriously? That's the only thing you care about? You post a comment on my picture, but say ABSOLUTELY NOTHING related to the picture? If you don't care about the picture, why should I care about you wanting a request? (It doesn't help that in most cases the request is nowhere near similar to the picture in question or the stuff I usually do)
Now this isn't about "asking a request" itself. If the comments were something like "Hey, cool picture dude! It's okay if I ask you a request?", or "nice pic", then I reply "thank you" and then you reply asking for a request, then it wouldn't be so bad. But still, avoid doing that.
So, if you want a request (whenever I'm taking them, NOT NOW) either do it in my profile or via PM. The comment section of the picture is just to talk about that picture (or stuff related).
If somebody comments on a picture to ask for a request, I will NEVER make a request for that person again. I said.
Have a good day everybody.