I have no desire to besmirch Parr's vision but two things are worth pointing out:
Popularity is not a measure of quality. If it were, Burger King would get a Michelin Star or two. His work was, I think, popular because the topics were pedestrian and the subjects every-man. That's not a dig, some of it is quite entertaining. See also Elliott Erwitt et al.
The post 1960s Art School and the arts business that ensued produced an ethos that promoted this sort thing. Wildly so in some cases. As one example see the work of Joel Meyerowitz. I find his work banal to the point of pain, but the New York hoidy toidy crowd drooled all over him and made him a star. I find Parr a far better exemplar of this sort of photography, but to each his own, I guess.
P.S. I wish someone would make me rich buying my most boring pictures. I can do tedious with the best of 'em ...