It may have something to do with perception and your level of skill and knowledge about computers/homes. I notice a lot of individual PC sellers will leverage the added value of all the software, drivers, etc. being updated and configured, and the Junkware clean out. Some people are also looking for a PC configured for a specific use, e.g. gamers, small businesses, students, retirees, etc.
Until recently, Most used computers from Dell and the big box retailers came with everthing installed on the defaults. Including the Junkware. Some people look at the time savings vs. the level of skill or effort required to fix up or configure the PC to where they are comfortable. They are willing to pay more for their lack of time and/or skills.
Just my anecdotal experience. Sounds more like houses all the time...