This is likely due to the more social nature of the format as well as the pre-constructed decks that typically come out with new releases, as they make getting into Commander much easier overall
Im only going over a few that scream out Build around me!! as they do something new or consistent
Creatures that would be awesome to splice with Colossal Dreadmaw include Cold-Eyed Selkie, Blight Mamba, Trygon Predator, Blighted Agent, Predator Ooze, Baleful Strix the list could go on and on
For creatures, the pure haste and +1/+1 is better
Its a horrible post-Wrath play or play onto a naked board or alongside great utility creatures such as Birds of Paradise and Noble Hierarch
Selling to an LGS is usually pretty easy: Just go to a store near you and ask what their policy on buying cards is