I could understand this, but it wouldn't hurt for them to tell me that.
I've had quite a few requests that people have made of me, and I've always tried to reply to them one way or another. I will admit, I do tend to drift in my work..... sometimes, I get to it right away, sometimes I am busy and it will take a while (and I do try to tell them that up front..."I've got 5 other things on the burner so it may take me a while to get back around to it" or whatever), but I do try to keep them in the loop. I just hate the "no response" thing. Of course, to say you will and then just disappear is wrong. If something comes up (or interest is lost), courtesy dictates "Hey....I've got other things that have come up", "I'm running behind, and it will take me a while to get to it", or "I'm just not interested in doing this anymore." Don't just leave someone hanging like that...........