Because you have to work with the user and session management of phpBB or vBulletin. This will influence many features such like usergroups, upload, registration, who's online etc.
ok. so basically what you're saying is: if you hack your board upon each upgrade you will have to hack it again to integrate it with one of these products. that's a given. probrably best done as an external project by some 4image *hackers*. i think you have a nice base with your current comment system. if it had more advanced features similar to vB or phpBB2 that would really take it to the next level. also the NetPBM option that i mentioned would benefit a lot of ppl. some ppl don't have the option to install GD or ImageMagick b/c they don't have root access.
Great, if i need help i will contact you....
gr8. i'll look forward to it.