It’s the same business model as consulting firms. Rather than hiring a few people for 65k each, a VP will bring in a consulting firm for 10M and get a bloated, half-working solution that costs even more to get working. The VP doesn’t care though because he ends up looking like a big shot in front of the other execs.
There are lots of developer agencies that hire developers as contractors that companies can use to outsource development to in a cheaper way without needing to pay for benefits or HR. They don't necessarily make bad quality software, but it doesn't feel humane.
Unless we're talking about some sketchy gig work nonsense, the "agency" is a consultancy like any other. They are a legitimate employer with benefits, w2, etc. It's not like they're pimps or something!
Those devs aren't code monkeys and they get paid the same as anyone else working in this industry. In fact, I think a lot of the more ADHD type people on here would strongly prefer working on a new project every 6 months without needing to find a new employer every time. The contracts between the consultancy and client usually also include longer term support than the limited time the original dev spent on it.
Agencies commonly use 1099 workers, there's been fierce legal battles on qualifications of agencies. (ABC test)
I believe 1099 worker growth has been outpacing hiring for several years.
The VP doesn't care because the short term result is worth more to the business. The business is not going to trip over dollars to pick up pennies.
Would you prefer that they hire, string those people along, and then fire them? That's a pain in the ass for everyone.