I don’t think there’s one simple answer to the question.
Yes, when addressing a performance concern I like to see what’s in the pan. But there’s also a cost concern. Take a typical family truckster like a Chevy Tahoe. Labor to R&R the trans pan is something like 2.2 or 2.4 hours. At today’s labor rates, a simple pan service will be $600. If I can do a fluid exchange for half that much, that’s an attractive option.
And I’m not even talking about the Ford Transit vans that have a 5.4 hour trans pan service time.