Blame this.
Corni
Most people don’t realize that dryads were only one of many species that were, broadly speaking, a magical combination of animal and tree. This is probably not too surprising: not to be indelicate about it, but humans tend to notice right off the bat whether a particular supernatural species can be, ah, interacted with without risk of later social ostracism. The ones that are not tend to fall through the taxonomic cracks.
Corni are a prime example of this: they are dogs that are magically linked with a particular species of tree. An unfortunately rare species of tree, even at the best of times; and in these, somewhat magic-poor days, Corni trees are virtually extinct in the wild. The few that exist are invariably found in areas that are under the personal protection and influence of an extremely powerful magic user, or a moderately powerful circle of magic users.
Which is a shame, as corni are invariably friendly, happy, plant-eating dogs that can live up to two, three hundred years. And that’s probably why modern-day magic users go to the trouble to keep corni trees alive. When you have an extended lifespan yourself, the mere decade or two that regular dogs live can be even more depressing…