Why sign him? What does his experience amount to? He's never worked a huge main wwe televised production in hd. He's not proven he can travel on a wwe schedule. He's known to have locker room problems and they've been treating NXT like an actual school with classes, teachers, instructors, and all.
Why pay them a sizable downside when you got guys like Nevilla and Graves with better looks, younger, cheaper, and who can work a wwe style without backstage problems?
You've presented no business argument other than they are skilled. So what? This is the real world, guys are skilled out there every day looking for 9-5 office jobs but that doesn't mean they should just be brought in, or even brought in and not start at the bottom of the ladder.
AJ Styles is phenomenally skilled, but his ass may as well read unemployed. You don't see njpw, aaa, or cmll offering the guy big guaranteed money. You don't see wwe trying to sign him, hot shot him to a main roster, let him headline some NXT shows in Orlando, or saying we will match what TNA was giving you. You know why? At the end of the day the asset of AJ Styles isn't drawing viewers, he's not putting asses in seats, he's not getting money out of wallets, not cutting amazing promos, doesn't have a great body, and they don't want to ego check him possibly from years of being a guppy in a pond .... Now take that logic and apply it to Richards but add in the fact he's worse than AJ and less notable to boot as is his partner.