There are cases when a practitioner explicitely acts as part of an organization that is not the actual service provider.

So it would make sense to be able to represent

• the practitioner's actual hospital or practice where the encounter takes place as Encounter.serviceProvider and

• the practitioner in his context as the Organization in who's name he acts as Encounter.participant.individual(PractionerRole).

One example of that are the German "ASV teams" which are official, registered, permanent interdisciplinary teams of practioners. These are typically spread across multiple hospitals/practices and every practitioner may be part of multiple ASV teams.

Every ASV team is an Organization and the practitioner's membership is a PractitionerRole.
An ASV team is not represented as a CareTeam here, since the actual list of team members is usually unknown to the local systems. Typically only the practioner's ASV team numbers (aka identifiers) are known.

Using CareTeam would also not solve the issue of representing the single practitioner in his ASV team context. Allowing CareTeam to be referenced from PractionerRole might solve that point, but would still require PractitionerRole to be referenced from Encounter.