It seems that the majority of professional arborists favor friction hitches that are tied with a free cord rather than a loop:
This is often tied using an eye to eye hitch cord like this:
This is a Blake's hitch:
One can also tie an asymmetrical Prusik without access to the end of the rope using one of these cords. As far as I know none of these are popular among rock climbers.
Some people do not carry any dedicated Prusik loops, relying only on runners, but I have seen enough climbers that do. For those that are carrying Prusik loops why not a single or double eye hitch cord?
I find ascending a rope with a Purcell and a waist Prusik challenging enough. If one of these arborist's hitches works just a bit better why not consider it?
I think it is valuable to know that one can tie a friction hitch using the end of the rope itself (Blake's) even if this wouldn't be a typical application; it's another tool in the toolbox.
Am I forgetting other critical uses for a Prusik loop that an eyed hitch cord cannot perform? Are there other practical reasons to choose a closed Prusik loop over these hitches, or is just a matter of different culture and experience? (Splicing eyes is not a typical climber skill from what I gather.)