It is truly rare for me at an Orchid show or Open house to pick up an Orchid potted up in Sphagnum. The last time I did that, I asked to vendor to take it out of the pot and show me the roots. He did! They were fine in this case.
Sometimes young plants are sold potted up in mixtures of small bark and chopped Sphagnum, I am not thrilled about those either, but I have made exceptions.
So, walking around the vendor tables, I walk right past those tables where the vendor has the table loaded up with pretty plants in Sphagnum, knowing very well I need to repot them or mount them, asap, thus disturbing them.
There are reasons I don't like Sphagnum - in my hands this stuff kills the roots within a few months. And on a couple of occasions I bought a plant wrapped into fresh Sphagnum, only to discover at home that the vendor had wrapped fresh Sphagnum around old Sphagnum and there was not a live root left.