Unpopular view; What does the WRC, teams, manufacturers, etc get out of their visit to the UK? Would they be really disappointed if it was dropped?
It comes and goes without much fanfare - and is pretty much ignored by mainstream media. There must be other countries were their media would be all over a WRC event. And Manufacturers are in the sport primarily to sell cars - and for that they need publicity.

Two points:
1 - Wales won't/ can't continue to back the event - they've bankrolled it since 2003, that's a good run; that nobody else has been willing to step in is an indictment on the sport & event.
2 - With the restrictive route regs, the organisers hands are tied with what they can do with regards to service park and stages used.