For one, it creates a negative incentive for the regulatory roles. Now people will seek to be head of the SEC just so they can score a specific job after. Incentives are misaligned.
Lots of private sector companies (especially law firms) include non-compete clauses for similar reasons. They want to prevent their former employees from leveraging their insider information against them.
An IRS employee becoming a tax advisor is one thing. The head (and more broadly executive level personnel) of the IRS becoming the head of accounting of a major firm is another.
I just don't see the misalignment in incentives. Everyone is thinking about their compensation next job, and it is only a problem if being bad at your current job somehow makes you more attractive to your next employer.
Unlike the private sector, there shouldn't be any insider information to protect. The SEC should be transparent about the law.
I have 0 doubt in my mind, anyone in that position wouldn't already be predisposed to believe that actions (regulations, enforcement etc) that help Robinhood (and other trading platforms) are a good thing and will work for those corporate interests because they share the same beliefs by default.
Then, once they leave the SEC, they're welcomed back with massive pay as a thank you for the job they did pushing Robinhood's agenda forward which is at odds with good governance principles.
Its like making the head of Exon the head of the govt's renewable energy initiatives. They're gonna say increasing renewable energy output isn't a worthwhile pursuit, what we really need is more oil. Let's sign a big contract over with exon, I even know the people who work there and can make it happen!
Working against society's interests in favor of the corporations
I work in a highly regulated industry and think that the cop and robber idea people have is out of tune with reality witch is more collaborative. Most agencies want businesses to succeed and actively work to help them do so within the confines of the law.
Its the same reason you wouldn't let a Defence contractor CEO be secretary of defence, or why you shouldn't let a telecoms lobbyist run the FCC.
Oh wait...
The best person to give advice on a subject are those who have experience on both sides.