DLR's bread and butter is with APs and guests who visit multiple times a year.
WDW is more of a destination where most guests visit once in a while or do once in a lifetime trips.
DLR can get away with having their HM overrun with NMB4C for a few months in the year, where as WDW would have a lot of unhappy guests if such an iconic ride had that kind of facelift during what could be their only visit to WDW ever.