We have windowpanes because glass used to be really expensive. Panes allowed us to use smaller sheets, with the added bonus that if one broke, you could simply replace part of the window.
Today, big sheets of glass are much cheaper, and many windows feature fake panes of glass–a process that uses one big sheet with moldings crisscrossed over it. Of course, this actually costs more to create than a simple window would. We’re overpaying to reproduce the effect that we originally put into place to save money.
If you look around, you’ll realize that we make choices like this all the time when new technologies arise. Cruft is a comfort.