Internal charging promotes LEAN capacity planning.
LEAN is intended to counteract wasted capacity. In many project-organised operations (including agile), wastage is equivalent to 2 - 3 working hours of each person each working day.
(No - Lean does not mean optimising flow, other than in manufacturing to optimise machine capacity.)
'Free resources' is one of the reasons for this inefficiency. The second mistake in creating teams is to take it too far by dedicating the team to a portfolio and also speculating that the team leader will take over the role of the line manager. This is turning the clock back at least 20 years by recreating silos of "my resources we need for ourselves".
It doesn't have to be that way - with transparency through digitalisation, it's easy to create a virtual organisation where strategic management and self-management go hand in hand. With internal charging, it is perfectly possible to optimise the use of resources. This not only increases efficiency but also increases motivation through the 'game' effect that automatically occurs at all levels. Similar to golf where even I, with my handicap of 30.2 am happy when I manage to play at my handicap!
The paradigm shift: planning optimal capacity planning with projects or Lean Portfolio instead of planning projects with resources.