>>27718951More people know gen 1 designs, they are more iconic. This is not pandering, it's not being stupid. Only a few really popular designs from later gens, such as the RSE starters, Togepi, Marill, Pichu, ect tend to be featured in a lot of generic 'pokemon' branded apparel.
For example if you look at the merch for XY a lot of it had the original starters with the new ones on it, it's largely because they know that the people who played pokemon when they were kids aren't going to recognize Chespin or Fennekin as a pokemon when they're buying a backpack for their kid.