Appliance based DVRs are turn-key solutions. I hope we both agree setting up a Linux box, obtaining a compatible OTA tuner, downloading and configuring Jellyfin all on hardware that is easily integrated into a general home entertainment setting is not a trivial task that most non-technically inclined folks can accomplish.
I personally ran PC based software DVRs for many years predating Jellyfin, but even in those years we had a Tivo for the wife.