But we see that you've noticed and I think the folks working on HHVM internally will get that corrected soon!
There are even competing PHP compilers/interpreters/runtimes now like there has been for a while with other languages.
I'm guessing there is some benefit to running HHVM on the type of large scale deployments Facebook has or there wouldn't be a need to keep it around.
The cost of rewrites at that scale certainly has to be far more expensive than the cost of paying a team to maintain HHVM
Hack was heavily optimized for Facebook-sized setups and was never intended to run in the places that PHP is most often run from (such as cPanel servers), so it never really picked up much traction among the PHP world.
Non-PHP developers never even considered it as an option, as they probably didn't consider PHP as an option either.
Basically, it was one of those projects that may have been a good idea when it was released (although perhaps just contributing more to PHP might have been the better thing for Facebook to do, but that's a different story), and it's time has now passed. I'm just surprised it took this long for them to end work on it, honestly
Or nobody cares about Hack anymore?
PHP usually ranks pretty high on many "developer hate" polls, so it's not too shocking to me that Hack never got the hype of React or Golang.