It is way more complex than that.
Harman/Ilford may have the money to do the work for a big seller like HP5+ - because of the estimated time it will take to achieve a return on that investment - while not having the money to do that for a niche within a niche product like Ortho film.
In Kodak's case, their volumes for something like Gold 200 or Portra 400 are much higher than the likely volumes for HP5+, so those return on investment calculations are different in that way. And Kodak's volumes for Tri-X are lower than the likely volumes for HP5+, so those return on investment calculations are different in that way.
One additional benefit that Kodak enjoys, but I believe Harman/Ilford lacks, is that Kodak already manufactures PET substrate themselves, in relatively high volumes.
All of these sorts of decisions are based on return of investment calculations. If they weren't we would still have 220 film.