Clothing stores are too. Most people want to try on stuff first. Personally I buy a lot of my clothes online now. I find something I like then buy it over again directly from the maker’s website (Lee, Wrangler, etc.).
I wear a specific brand and style of sneakers, and have for 30 years or so. Because they aren't trendy, stores don't sell them. I used to get them through Amazon. But now I do what you do. Instead of going to Amazon, I buy them directly from the Saucony website. It's less expensive, availability is much better. They even seem to be higher quality, more like the sneaker originally was a few years ago.
Is it possible corners are cut for some Amazon merchandise? That's pure speculation.