1. The Houston Rockets won't really be able to get off of Wall's contract
The primary reason why the Rockets would be wise to keep Wall is simple: they won't really be able to fully get from underneath his deal anyways. For all of the talk about a buyout, players don't usually give back much in a buyout, and understandably so, as they've earned every dollar that's been given to them.
Even if you're of the faction that believes that Wall never should have received the designated veteran contract extension (AKA supermax) that the Wizards gave him in 2017, he was eligible for that deal based on the NBA's rules, which state that a player has to be with the team he was on at the end of his rookie contract and entering his eighth, ninth or 10th year in the NBA.
The player also must have demonstrated that he's one of the top players in the league, which in Wall's case was demonstrated by making the All-NBA Third-Team, which he qualified for in 2016-17. Wall wouldn't be wise to give up anything significant in a buyout because he surely won't receive a deal with an average value of $40 million again, regardless of how much longer he plays.
And especially considering the fact that he's worked tirelessly to get himself back on the court, as injuries such as the ones Wall has suffered require an extensive amount of rehab. So a buyout would likely not be something the Rockets would want to do because they'd be paying him a hefty amount just to go home, as opposed to utilizing him for whatever contributions he can bring to the team.
As it pertains to a trade, the Rockets would be forced to match salaries, meaning they'd also be stuck with another bad contract on the books. There aren't many teams that have a need for a point guard that would also be able to construct such a deal, with the LA Clippers possibly being the only remaining option.
And even the Clippers just brought back Reggie Jackson and may not view Wall as a significant enough upgrade over Jackson to justify taking on Wall's deal. But even if such a deal was to be had, the Rockets would almost certainly be stuck with Luke Kennard's $64 million owed over the next several years (unless they traded it for another deal, which could be difficult, as he doesn't have a ton of value).
So in essence, the Rockets would never be able to fully get from underneath Wall's contract, and with just two years remaining on his deal (one guaranteed year and a player option), the best call would be to stand pat, rather than taking on someone else's deal, with could have the franchise handicapped for longer than that.