Why don't tax prep companies like H&R block create a salary review website?

Your post doesn't show your TC. This is your only warning. Please correct this next time.

And they should because.....?

It's a lot of headache with differential privacy and allowing their clients to opt-in/opt-out of this service. And what incentive is there for them? Selling their clients' salary info? Seems like bad PR

cuz they don’t know ur level / role