Yes, if rail were so good all the families and normal people who value there lives could take it, meanwhile the interstate could go turn into no speed limit chaos where all the rich people with huge egos and small dicks can crash their Porsches into each other without killing an innocent person whose just trying to get to work.
I think it’s a bit disingenuous to compare Austin building rates to SF and NYC. Austin is far less built up then those other two cities so there’s still a lot of easy gains to be made. Turning two single family homes into a 3 story 10 unit apartment complex is relatively cheap, has a high profit potential and multiplies the housing stock by 5. The problem comes when you run out of cheap single family houses on large lots and have to start turning the town houses and three story apartments into high rises. That is significantly more capital intensive, requires way more permitting and inspections, as it should, and has less potential for gains in housing and profit.
This isn’t to fully excuse those cities as they could definitely be building more housing. Just saying their success isn’t only due to them getting the government out of the way and letting developers build. Building 9x more housing is easier when your 9x less dense already. San Diego has no excuse though.