people are often regretting on using my desktops for my system
Do they try to use it and hit roadblocks or do they know it’s a different system and do not want to try?
If they are trying, it might be helpful to know what apps they need/want to run when becoming frustrated. Otherwise, like the other comment suggests, it might be a psychological barrier.
If they do not want to try, maybe play some music, videos or games on the debian machines and see if they engage. If it only POS and inventory apps it might be more difficult, especially if they have to work with files, printers, emails and so forth.
Also, are they usually busy and/or stressed when needing to use the machines or can they take their time? If they are with a customer and trying to overcome linux challenges that could be frustrating.