Because it’s almost always superior, if you need things from more than one “niche”. Specialty shops only make sense if you have a big order in that niche, like building a new PC. If you want a hard drive, some TCG card sleeves, some zero cal food products, and wanna top up on boxer shorts, Amazon is just too far ahead.

I have tried other “everything” retailers in Europe, like Otto, but their selection for everything is tiny. Ironically, it’s not tiny well selected, well known european brands. It’s still filled with Chinese shovel ware.