Why do some games have easy installations for mods while others make your brain stop working because the installation is complicated and you sit there for hours looking through the guide to set it up right! AAAHHH!!
Because the first group is looking to support their player base (and aims to make money long term by developing loyalty and expanding that base), the second is looking to drain as much money as possible now without concern for the reputation of the publisher. [Or they could just be incompetent ¯\_(ツ)_/¯ ]