Why so much sales hype and advertising about replacement windows?

Why so much sales hype and advertising about replacement windoiws?  

Have you ever wondered why there are no ads for "replacement fireplaces" .. or "ill fitting or missing dampers" ? These items leak more heat than all your BiltBest windows - but salesmen don't leave flyers for new dampers in your mailbox, do they? WHY? ..

One reason homeowners replace their original BiltBest windows is because they can immediately see a difference when a window is replaced - DUH? Even though a project like sealing air leaks with installation of new weather strip may be all you need .. and many times save more energy than total replacement windows - there is low demand and talk for air sealing and weatherstripping services.