For all it's problems, and it has loads; F1 still gets massive exposure, that the WRC can only dream of. It's why Manufacturers will still sign up.
We've just had 3 fabulous seasons with the 2017 WRCars - Toyota and Hyundai have thrown everything at it (and maybe more) to win. Citroen haven't had the budget they once did - and it has shown. M-Sport do a great job, but struggle because Ford don't commit financially like Toyota & Hyundai.
I think some people have been blinded by All Live; it's great for the hardcore fans, but not enough other 'free to air' coverage is out there. And Manufacturers, sponsors, etc want as many eyes on their product as possible.