IMO everything in the action must be trued with all cuts in referance to the boltbore axis. The bolt being held in perfect alignment with the chamber/throat/bore being the ultimate goal while lugs are seated symmetrically on abutments. I see refitting the bolt body front and rear a necessary step to ensure positive alignment and perfect lug engagement. How imperfect everything is if this is not done is up in the air and would depend on the specific rifle, and much like Shawn said, it will always be in question as to how much better it could shoot. I'd rather know that a customer's rifle is 100% true for less than two hours more work into it. To me, it's just peace of mind knowing my rifles are all built the same spec's and have 100% done to them that could have been. I know where "I don't" have to look for problems is what it amounts to, so that's the only way I'll do them. The reason I won't just "install" barrels, or any other work that I feel is a half way approach. Most see service as doing only what a customer wants done, and that's fine too, just not my approach.
Many want to sell the rifle at some point down the road, and I certainly wouldn't blame anyone for putting money into a custom action instead. For many it's just more feasable to use what they have for a little more cash into it, or some may have no plan on selling so it isn't about that for them.