JIP or lack thereof

Like it or hate it, I’ve actually become expectant of JIP. So when Harvest is voted for a 3 out 5 members quit immediately on map selection, I expect it will be only a short time before JIP throws me a few teammates.

Four games of CTF on Harvest today, nothing, 5 on 2.

So, why does JIP sometimes not kick in, does anyone know? Is it a crimson map pack issue?