FOC became the rage with carbon arrows. I shoot aluminum arrows which are not as stiff when compared to carbon arrows so I don't really pay that much attention to FOC. Since I do shoot aluminum arrows, I pay strict attention to GPP instead. I've shot aluminum arrows from 2114, 2212 and 2213 out of my 37# recurve and 2212, 2213, 2215 and 2117 out of my 42# recurve so GPP can be quite heavy.
Right now with my 42# and 37# recurves, with both bows shooting the same light 2212 aluminum arrow, but with different brace heights, I'm basically shooting 14.1% FOC. Both bows shoot a good GPP arrow wise with the 37# recurve shooting, as of right now before I try and tweak it some more by adjusting the brace height, 13.00 GPP.
So, if one chooses to shoot carbon arrows, they'll always have a high FOC arrow whereas one who shoots an aluminum arrow won't have a high FOC number. But, the carbon arrow will usually have a lower GPP number than an aluminum arrow.
In essence, a trade off.