True, but things are in motion to alter or dismantle required facilities for flying them, so keeping them in mothballs won't do any good. Plus some of their hardware is overdue for replacement and no one manufactures it anymore. STS isn't just an airframe, it's the entire system of ground infrastructure and the engineering network stretching back to the contractors' factories, all of which is going away.
Personally, I'll be happy when all the orbiters have completed their last missions, brought their crews home safe, and are safely tucked into nice climate-controlled museums. I've seen Enterprise up close, but she has fake tiles and engines. I want to see the real stuff.