Unless you're WoW, 92,160 subscribers is nothing to scoff at. Assuming all plots on all servers are taken, that's 60 plots x 8 wards x 3 residential districts x 64 servers (that's how many I counted on ARRstatus). That's roughly $1,381,478 a month (assuming all are one month recurring full subs without legacy status).
Of course, that's not accounting for Free Companies which can be owned by someone that also owns a personal house, and the fact that FC houses can be refreshed by any of its members. Still, even if we halved that amount, it's not so insignificant.
That said, it was a feature that should have been in place from the beginning, and while I'm sure keeping homeowners subscribing wasn't their primary reason for implementing it, I doubt the possibility of reclamation helping to retain subs didn't escape them either.
