A .psd file is not an end-user asset. I can think of no use case where someone would point a browser at a hosted .psd and expect that binary file to render as an inline image.
A .psd file was, for a good chunk of the past twenty years, the "de facto standard" file format for teams or entire departments of graphic artists who spent all day, every day in Photoshop. I once worked for an online ad agency and Photoshop was used more often, by more people, than MS Word and Excel combined. The Network Effect was in full force. Graphics teams at three different companies cooperating on the same campaign would assume that their counterparts were using Photoshop, and would expect to send and receive .psd files. Man, Adobe must have been printing money in those days.
If you worked in print publishing, digital publishing, advertising, marketing, there was probably a graphics department of people who spent all day in Photoshop... and an IT department that was constantly trying to add new server capacity as fast as those artists were consuming it. Back when we measured server storage in GB, not TB, fifteen different versions of the same massive PSD file could cause real heartburn.