They're not trying to incentivize people to move to SF; they're trying to maintain a competitive hold on the market of talent which is already there, as the realities of our current climate are that many of the highest-talent candidates are to be found in that pool.
If they're ok with people working remotely, they'd do much better to pay everyone as if they lived in a very expensive area, and attract all the people who don't want to give up a lot of the flexibility of a large paycheck but would love to be able to save even more of it by living somewhere cheaper.
(Their calculator also seems somewhat bonkers (on the extremely low side) compared to the local market where I live. It seems based on a somewhat-arbitrary, quick-and-dirty-wild-guess estimate formula vs what real, on-the-ground competitor companies in those areas are paying.)
EDIT: there seems to be a small trend emerging where every company I've seen with fully-public payscales/pay calculators wildly comes in below what I'm currently making, and what I've heard from local competitors. And I'm not in SF. Wonder if there's some causality there, though it's still just a handful.
Also it's amusing to get a downvote for offering up the info that Gitlab would want me to take a pretty substantial ~30% haircut in base pay based on where I live. What would be attractive to me would be "we'll give you 80% of your current take-home, but you get to live wherever you want," but this is basically the opposite.
