The largest tech companies could also implement a shared cert program via some kind of industry group, with periodic re-certification requirements. This’d surely be far cheaper than all of them running multi-stage leetcode and system design interviews, and they already basically publish study guides so this isn’t even that different, just cheaper for both the businesses and candidates.
It’d also make job hopping far less painful (see above: cheaper for the candidates) which is why they don’t.
So we may conclude: the point of leetcode interviews is wage suppression.
Never gonna happen, as they outsource this certification to universities already. They're not going to stand up their own cert programs to streamline the process; the muli-stage leetcode interviews are about hazing culture and making sure employees are servile, not merit culture and making sure employees are competent and qualified.
Like you said, tech companies need candidates to feel like they barely passed a grueling interview because it makes them wary to jump ship and have to go through that again, not that they are well qualified industry professionals who have the credentials to move between jobs and work anywhere they are certified.
It’d also make job hopping far less painful (see above: cheaper for the candidates) which is why they don’t.
So we may conclude: the point of leetcode interviews is wage suppression.