The reason (that you don't recieve answers to requests) is probably a combination of a couple factors.
1) Most modders bristle at requests. We get them a lot, and sometimes they're pretty unreasonable (not saying yours are). As a result, the reflex reaction to any request is pretty much going to be "no."
2) Most requests that aren't unreasonable are pretty simple/have already been done. In those cases, they'll get ignored because a lot of the time no one wants to have to keep repeating either how to do it or where to find it - because a lot of the people making requests tend to be lazy about the easy stuff and that's a real turnoff.
Now, I'm not saying that you necessarily fit into the "stereotype" modders will apply to people who make requests, but making any requests at all is a tricky thing. How can you get your requests answered?
-Ask politely. This should be easy; few people will jump up to help someone who's rude about needing help.
-Make sure you've looked hard for a solution / whether it's been done already (and make sure you make mention that you have in your request). Requests are a lot more likely to be fulfilled if it's obvious that the requester has made a sincere effort to get it done.
-Don't make unreasonable requests. What's unreasonable? New player models, new maps, complete mods, that sort of thing. Keep in mind that dozens of hours go into making those kind of things, and that's a lot to do just at the whim of someone else.
-Be a contributor to the community. A lot of times people will come in to GT and their first post will be a request. Unless it's an asset that already exists, I don't think I've ever seen a request like that filled. If you're already active in the community, it's many, many times more likely that someone will be willing to help you.
Now will that guarantee that your request gets answered? Of course not. There's no guarantee that your requests will ever get answered (it's not that way for anyone) - but doing the above will certainly help. Best of luck finding what you need!