Buying online direct from the manufacturer? Almost everyone sells direct. Use Amazon to find the seller and then contact them directly.
What if you want to buy simple Chinese plastic stuff (e.g. someone elsewhere mentioned zip ties)? The manufacturer is somewhere in China with a minimum order of 10,000, so no, you can't go to them. Amazon is often the cheapest source for this, cheaper than any local retail.
Amazon delivers next day or the same day many of the items if you have Prime.
I tried many times to order something directly, and most of the time it’s the same price and longer shipping. So, for me in terms of convenience Amazon wins.
Why would I do that? Now I’m spending time verifying individual random brands all to get the same price (plus shipping)?
You gave me the idea to buy something I was thinking of ordering from Amazon (a Time Timer) and see how it compares. The timer I got is $24.95 on their site, 15% off welcome discount (-$3.74), +$10.00 shipping, and "orders ship within 3-5 business days." On Amazon they have the one I ordered for $19.95 list price minus 15% = $16.96 and I could have it within 1 hour for $9.99 (lol... I've never seen that option before) or tomorrow for free, although I do have Prime which is why that's an option. I do like to buy a lot of things directly from their original sellers or a specialized store (Loop earplugs, or speed cubes from TheCubicle, electronics from adafruit or jameco or digikey, etc...) but it shows you a big difference in service level.