I think the big picture answer is this:
If you're doing the work yourself, then you probably don't have a balancer, so you would have to do somewhere, so why bother unless you have a vibration?
However, if you are a shop and this is a service you are providing (for a fee, of course), then it's best to do the balance, if though it is unlikely to be necessary. This just protects the shop from those customers who can never be satisified, (or whatever, you know what I mean).
If you are a customer in the above paragraph, then it is probably unnecessary, but it's part of the procedure the shop is doing, so you either pay for it or find another shop.
Hope this helps.