Ask HN: Why isn't team-based engagement more popular in tech work?

For example, to build your web-app you hire a team (backend, frontend, all-end, QA) all as a unit.

1. team could have more negotiating power vis-a-vis big-co 2. worked together on multiple gigs (hopefully), 3. fewer interpersonal issues (again hopefully) 4. know their tasks on the team from the get-go. ..many more.

why isn't this more popular?