So why would you buy it off of Anthropic?
I don't understand the question. For one thing I use local models mainly, but even if I didn't, I'd be buying the tokens from cloud model providers, not the prepackaged, fully complete software itself. I buy the tokens to make what I want.
It's actually quite similar to buying the services of a programmer off Upwork to build something for me, only with LLMs it's way cheaper and faster, with a shorter feedback loop.
Interesting that you think building is just coding.
What do you think architects do? Or interior designers? Or civil engineers?
In any activity you can take shortcuts that makes it easier. It's up to you how many (if any) you want.
Take woodworking for example. When I build a kitchen cabinet, I can get lumber that's already smooth and treated, I can buy drawer tracks, I can use power tools instead of a handsaw and a screwdriver, I can use a pocket hole jig to make joints easier. I still have to do more planning and assembling than with the Ikea cabinet, which also takes more work than having a contractor do everything for me.
I'm doing it my way because it's fun for me. Other people might enjoy other parts of the process - or different things altogether.
There's a whole spectrum between doing everything from scratch and paying someone to have it done for you.