On driving factor is the (over)use of antibiotics in animal agriculture. It's weird the article touches this issue in just one sentence...
"Over 70 percent of antibiotics sold in the United States are given to livestock, including cattle, which translates to significant human health impacts."
"Unlike with human medicine, however, antibiotics are often fed to cattle as a preventative measure, rather than as a treatment."
"Antibiotic resistance in cattle does not only affect the health of the cattle, it impacts people as well because many of the antibiotics given to cattle are also used in human medicine. Eating meat or consuming milk from an animal with antibiotic-resistant bacteria may infect a human with that same resistant bacteria"
"I see the disinfectant, where it knocks it out in one minute. And is there a way we can do something like that by injection inside or almost a cleaning, because you see it gets in the lungs and it does a tremendous number on the lungs."
"I said supposing you brought the light inside the body, which you can do either through the skin or in some other way. And I think you said you're going to test that too... So, we'll see, but the whole concept of the light, the way it kills it in one minute - that's pretty powerful."
Long story short: bacteriophage are extremely difficult to fit in the current legal/regulatory framework of the medical/pharma world/system.
Bacteriophage are not stable compounds such as chemical molecules (antibiotics, etc...).
They evolve and change, adapting to bacterial evolution (or just spontaneously because we're talking about organisms, who sometimes just changes). It may be an advantage from a efficacity point of view, buts it's a big no-no from a regulation point of view.
This makes is harder to have real trials (even if things progress slowly).
Then you have all the biological questions about injecting live virus in an patient and the risk of immune response.
Then you have the complexity of both producing phages in a stable manner (remember: these fuckers have a tendcy to "evolve" on their own) as well as shipping them (require refrigeration all the way, contrary to antibiotic pills).
Source: bacteriophage were the subject of my master thesis, even if it was a while ago.