One significant problem is that teams have much more negotiating power than individuals. Which is why teams that stay together are consulting agencies.

To put it simply: The software development department of a company might bring the company $10 mil value. A consulting agency with great sales would bill them $9 mil to do the work. Individually hired developers might be paid a total of $1 mil.

If the company hires an entire team, eventually the team figures out that they bring $10 mil value and can easily negotiate their pay up to that because they coordinate together. Individual developers almost never coordinate like this.