People who aren't critical to the core product, or whose projects aren't big revenue generators. They might be high performers while being technically unprofitable.
Not necessarily a bad idea, but disrupting those business critical teams by just swapping out people could actually slow down execution and hurt revenue.
I'm implying that rather than laying off top performers you find them a different role in your organization.
Granted if the skill set is incredibly niche--such as hand optimizing HC12 assembly and you've moved to ARM then perhaps not.
It's hard to imagine a scenario where an entire project teams skillset is so niche that they couldn't find a home for top developers in other parts of the org.
You can't just swap out members of a team, or add more members to a team, and expect the result to be faster execution (in short run) even if the new team members are high performers.
In the first case, you're losing team members with tribal knowledge of the system and its requirements. In the second case, you're exponentially increasing the pathways of communication. In either case, you still have the ramp-up time for new team members.
Any number of reasons. They might be high performers in skill sets not needed in those business critical projects. You might be leery of the time needed to get up to speed on something completely different.