[CarlitoBrigante]

We also recommend vB 3.8.x to our clients and/or most of them simply do not want to upgrade to vB4. Among our clients there are some of the biggest vBulletin forums, and most of them are running vBulletin 3; in some communities, the users decided they did not want to upgrade to vB4 as they did not like the interface; in other communities, the move to vB4 was followed to a drop in traffic (in some cases caused by early adoption of vB 4; the first releases of vB4 were so full of bugs that users actually left communities enraged by the change).

vB4 has also many design flaws that are irritating and expensive for a website owner, so some clients do not want to go with it. I am speaking about the lackluster sidebar implementation, the stylevar system (which caused style edits to be more time consuming than on vB3), the separation of the CMS from the forum area (which can be minimized if you use vBAdvanced instead than vBCMS). Especially business minded forum owners consider these things very carefully; hobbyists owners running their forum just for passion often are more willing to upgrade.

None of our clients (we have a portfolio of about 50 forums right now) moved to different systems like Xenforo, as they do not want to force their userbase to a traumatic change.