"I'd like to move out of my rent-controlled apartment in SF because my job is in Mountain View, but I don't want to walk away from this rate."
Well-off-techies who somehow stumbled into both getting a grandfathered rent controlled rate, and a job in the next city over might be a majority of posters on HN[1], but are a tiny minority of the population. You probably shouldn't be basing overall public policy around them.
[1] I personally think it's unlikely.
I'd be interested to know the actual numbers, but I doubt they happen to be 90%.
Even if there was rent control both places, you'd have to find a rent controlled apartment in the new place. And in reality, you can't, because nobody is willing to leave their rent controlled apartments in the next place either.