phpBB is FREE and OpenSource.
vBulletin requires a new licence for each new version. We do not have a licence for versions 2 or 3 and have no intention on buying one when there is a FREE option that does the job just as well.
You say vBulletin has more features then phpBB?? Tell us what features you miss and I'm sure they can be added to phpBB.
[Insert witty motto or humorous IRC quote here]