I’m not into Lolita fashion myself, but this seems a similar to a discussion I saw about Dungeons & Dragons. Why spend all that time homebrewing a bunch of new systems and rules for situations when there’s another TTRPG system that already has systems and rules for those situations? Because some peoples’ enjoyment comes from tinkering with an existing product, adding onto it. They also get a starting point instead of having to build a whole new TTRPG, design and sew an entire new dress, for themselves. For some, it’s easier to see a pretty dress and change it to fit yourself than it is to think of a design for a pretty dress you’ll love as much. It’s easier to start a Dungeons & Dragons campaign and add on rules to tack onto it than to come up with a whole new campaign or rule set yourself, or to come up with the same campaign idea with the other TTRPG’s world as a basis.