>>10318389Lego consumers just want normal minifigs. These were proposed multiple times by designers, but Nintendo turned it down every proposal. A requirement for Lego Mario was that the main characters not be compatible with normal minifigures as Nintendo is super protective of Mario's image right now. The reason they were fine with K'nex figures is because they can't (easily) be disassembled and mixed/matched with other figure parts.
Also unlike every other theme in history, 99% of sets available are useless without you buying the one $60 "starter pack" set that actually includes Mario.