Rikutatis
There'd be no point for a guild to align if it could just be neutral and accept everyone.
Umm ... what about RP reasons? Sheesh, are people that out of touch with Roleplay these days? Oh, then there is faction TPs, faction items, faction events, involvement in government and so on.
Count me as a +1 vote. Little enough attention is paid to neutrals as a viable faction as it is so this would seem like a step in a positive direction. One of the reasons I've heard people cite they didn't want their guild neutral is that it limited recruitment and had no advantages.
Also, there is currently zero option for a guild to be both Hominist and Theist. This would allow that option.
(Edit: To add constructive points other than Riku has gone insane. )