Oh wow, I totally forgot about this thread! I'm sorry.
Welcome to the 2 newbies! It's nice to see more members on this side of the pond.Curiouser and curiouser! Spill the beans...
Well, the main reasons I feel it may be for me are:
1. I've never been able to imagine not being able to be with someone else if I had feelings for them, or understood why people don't do that anyway. One of my earliest memories to do with this was when I was about 8 and I saw some TV show where the boyfriend of one girl kissed another girl. I genuinely didn't understand why she was so upset. All I could think was "But he likes them both!"
2. The second reason is because I'm asexual, and part of me feels like it would be wrong of me to get into a relationship with someone, and expect them to never, or very rarely have sex. So I also feel I should allow them other partners to get those needs met.
3. And the final reason is, I don't believe one person can fulfill every need I have, and I shouldn't expect them to. Therefore, I feel it should be fine for me to seek elsewhere to fulfill needs that aren't being met, and vice versa.
Anyway, sorry for taking so long to answer!