Well Im just assuming repaints = more profits for Hasbro. Also less trouble coming up with a new mould for another character... but for same character repaints beats the pus out of me, mebbe as mentioned earlier = profits still behind as reason, coz lets face it, WE, are not the target customers of Hasbro.
It's the toy stores, who are targetted to buy the random repaint Hasbro offers up. Whether these shelfwarm or not is not anymore Hasbro's concern, it's the toy stores that have to make up for their losses.
Not all repaints are bad though, I can attest to that, at times better than original and even at times offer an incentive to the fandom
(Hasbro throwing us a bone from time to time) e.g. G1 colored Generations/Classicverse whatever Starscream which I really prefer over the first release only because I didnt like the stylized wing deco - I sold the Classics one shortly after. Another would be the generations minicons combiners repaint... if it werent for that I wouldnt be able to get them as the G1 originals are kinda pricy for such little figs seeing as well that these are jap exclusives on first release.
As for the reuse of BW to Armada - even though there's no gimmick when one does attach a minicon to them (ending up with minicons just look like unsightly over growths) I guess coz Armada ended up more of a lumped up homage line which carried on to Energon so it kinda paid tribute to both G1 and BW - using the names of old character in new molds/characterizations, but with the BW moulds the moulds are still useable and quite poseable really, so instead prolly of major new mould creation , a reuse was decided - again this is just pure speculation.
Then, there's the filer line repaints.The very first generations line (filler) was filled in by whatnot recolours and slapped with the random names that the people at Hasbro thought would fit
at times it works somehow - e.g. Nemesis Prime (Big Convoy) at times it just looks tacky as e.g. Purple Fuzor Silverbolt, i dont know what color Optimus Primal, eeeww - the bottom line is, for me, basically profit and cost saving
Wanted AM partner Vanguard, Myclones Dirge, G1 Victory Leo, e-hobby Dark scream ( the black version), e-hobby Magnificus
Parts- AM partner Basher-side guns, G1 Actionmaster Elite Windmill's blades[I][B]