>>34920769Because she's cute. She also has an actual [lot, even if it's not a very good one, and is closer to the main character of Sun/Moon than the actual main girl, who doesn't even really have a real name. Lillie gets all the attention from, GF, so why would it be any different here? If you push something hard enough it will get fans. Haters too (see Lucario) but lots of fans too.
They should've just gone all the way and made a Lillie Mode where you play as Lillie. Or let you unlock Lillie's clothes and haircut on Trainer Customization after she throws out her Nihilego themed dress.