If you could wipe out the past and start from day dot then /maybe/ you could transition without too great a risk; even then, you’re looking at a massive transformation project with a lot of temporary contract workers. It’s expensive, because billing fundamentally touches every part of a business - if it breaks, you can’t pay your service providers and you can’t get paid by your clients. Optics doesn’t matter here, dogfooding is a nice bonus and not a given. There’s just no compelling reason for them to move over.