The window industry is similar to the car industry insofar as you typically buy through a dealer as opposed to at a retail store. Of course, this isn't always true - Home Depot, Lowes and other specialty stores like Menards all sell the big national brands like Andersen, Pella, Simonton, Jeld Wen and Reliabilt to the general public. Often, they also offer installation through subcontractors who they typically pay per window, instead of hourly. The problem with this model is that the subcontractor is incentivized to install the windows as quickly as possible, instead of as thoroughly as possible. The system is not structured to benefit the long term interests of the consumer (again, not always, but for the most part).