The article is about prophylactic use in persons who have had a tick removed that was attached for more than 36 hours. It would have no impact on levels in the tick population (as it's given after the tick is removed) and should have no impact in the human population (considering how low the proportion of people with ticks attached for more than 36 hours is)
I'm not worried about tick-borne diseases in this context (completely agreed with your point there), but rather all the other things that doxycycline and similar drugs are used against.
Well I think the point is that using it for tick bites isn't going to materially increase rates of prescription / usage.
Doesn't seem like it would be widespread usage given the checklist they provide. Title is a little misleading; it's not just "a doxy a day keeps the lyme disease away!" or similar.
This would be of particular concern if Borrelia bergdorferi were spread from humans into the natural host pool. Without that, the selection pressure for a doxycycline-resistant variant of B. bugdorferi is low to non-existent.