I dunno... I think it's a gimmick although I would certainly have been drawn into it at some point over the years.
I have found, however, that keeping my hands clean and wiping them regularly with a towel helps more than ever to keep my strings cleaner and brighter for longer. If I feel that the strings do need more attention then I will clean one string at a time and then clean the fret board.
If I was a gigging guitarist then I would rather change my strings regularly. Probably a set for every guitar per gig. And I wouldn't do that, my guitar tech would.