Oil, OEM or use an aftermarket brand?

[Cutty72]

I have a question for those that have had bikes longer.

Reading through the Buell owners manual, and my SV's Service manual, they both say you only need to change the filter every other (buell) or every third (SV) oil change.
If you are changing the fluid, why would you not want to change what is keeping that fluid clean??

Personally, until I hear a good reason to NOT change it, I'll change with the oil... a few extra bucks for a filter isn't gonna kill me.