i'm polyamorous not because i'd think it'd be cool to have sex with lots of people.... i think when people hear you make such a statement this is the automatic conclusion... so i formulated my reasons... and for me there are two...
1) i don't like the perssure of feeling like i have to be everthing to somebody... in an open, polyamorous relationship, i don't have to deal with that pressure, or the guilt associated with not being that person - yet still have the opportunity to love and be loved by that person... it's ok that i'm not some sort of mythical soulmate... where i and a partner diverge, there can be room for others to pick up the slack.... i sometimes think that i'm considering myself to be polyamorist not because i want to be able love multiple people, but because i want to give that to my partner(s).... so that our entire romantic involvement is not riding on just me, or just her.... we can be free to love each other at the level the relationship seeks on it's own, without conjuring expectations of what some exclusive, monogamous, happily-ever-after relationship should be....
and 2)
it has large part to do with my Myers-Briggs personality type of INTP... i'm more comfrotable in open-ended settings where there are options, as opposed to a closed one without any... not that it necesarily means i'm on the look out for one, just that it's comforting to know that it's there....