Whenever someone says that the reason some health related thing isn't being used because it's not patentable and there's no money in it it's a pretty sure signal they don't know what they're talking about. Therapy methods, manufacturing methods, etc. are all patentable. As an example here is a patent that was granted around methods for selecting bacteriophages against specific bacteria [1]. If you search patent records for phage therapy there are tons of granted patents.

The original patent for insulin was given away by it's discoverers because they wanted everyone to be able to have access to inexpensive insulin. That hasn't stopped pharma companies from coming up with patents around formulations, manufacturing methods, delivery methods, etc. and making tons of money off of insulin.

Sibling comments have pointed out the real reasons it's not commonly used despite the promise. I just wanted to point out not being able to patent something is almost never a barrier for pharmaceutical companies if they think they can come up with a profitable therapeutic.

[1] https://patents.google.com/patent/US10357522B2/en?q=phage+th...