hmm, i guess i might be out of the loop, but that seems like a legitimate question someone might have... ill answer it:
niche specific recips come from wanting more links to category pages to boost page rank and relevance in search results. some linklists insist on only niche recips, some give you the choice and some still have regular general recips, it just depends on the linklist owner and how important he thinks his list is.
personally i dont insist on any recip (if your site has no recips to other linklists that is) but i give you a better listing if you do and an even better listing if you give me a niche specific recip. i think far too often link masters get on ego trips and demand things that everyone would be happy to do if they were presented in a better light to the webmaster... no body likes loose/win situations, especially if its you who is on the loosing end, but everyone gets something if you take a couple of seconds to step back and evaluate the situation.
just my two cents at least
