For me, as I really only focus on collecting 3 main lines with a couple of notable exceptions:

G1 - I'll keep them if I get them but I'm not exactly seeking them - Unless of course we're talking about Scorponok or a MIB/MISB Soundwave.
Beast Wars - I want the Box/Backing-card, the Techspecs and the Instructions so if anyone wants to offload any of these, please let me know.
Classicsverse - Backing Cards and/or boxes and instructions.
Masterpiece - Everything.
Soundwave - Everything.

Packaging does take up a considerable amount of space, especially boxes, so unless they're really special to you or you've got the space to store them - I don't think they're totally necessary.