Personally, there are 3 reasons I'm never on multiplayer:
1) The evening/night GMT games are in the middle of the afternoon for me (I work most evenings, so its pretty much a total time conflict)
2) My schedule isn't consistent enough for me to name a good time for me to play and host games then.
3) My ping times for anyone not in North America are absolutely rubbish and my primaries are totally useless, rendering the game basically unplayable.
I know that the first 2 are basically personal problems, but the ping issue seems much more exaggerated than my experiences with other games would lead me to expect. Most of this experience coming from Freelancer.