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You mean "customers in the aisles means shorter lines at checkout"? That would be true if you're optimizing for short lines at checkout, but what a business is really optimizing for is sales over time, and so you want as many people to come in, buy their stuff, and leave in as short a period as you can. The more people you can get in and out of your store, the more money you make. The more time they spend wandering the aisles (or browsing your site), the more opportunity for them to say "I can get this somewhere else faster/easier/cheaper." Every second they aren't punching in payment details is a moment for the baby to cry, for someone to call, for the boss to give them an assignment, for a bathroom break. Any of those things can totally break the moment and cause the customer to abandon their cart and leave. Solution? Don't let them hang around. Get them to their goal as fast as possible and keep the total transaction time -- from landing on the site to checking out -- as short as you possibly can. To put a more concrete example, imagine a company like Instacart. If it takes you more than an hour to fill up your cart on the site -- for whatever reason! whether bad organization, slow response times, whatever -- then you might as well just go to your local grocery store yourself! You can almost certainly be in and out of your local store in less than an hour. The value prop that Instacart has is "you never have to go to the grocery store again, because it's easier to order from home." But if it's harder to order from home, then what's the value of Instacart? (Again, I'm oversimplifying here, but this is the gist of the value prop. Instacart doesn't sell groceries -- it sells TIME. It sells that hour of your life back so you can spend it with your family or playing video games or arguing with me on HN.) And so in terms of scalability, Instacart wants you to land on the site, add everything to your cart, and get the order placed as fast as possible. And to do that, everything needs to be fast. The category pages need to load fast, the product detail pages need to load fast, your cart needs to load fast, the checkout pages need to load fast. The faster everything is, the quicker -- and better! -- your experience is. There are numerous studies out there that show that as little as 500ms latency can cost millions of dollars for a company. It's really important to keep everything fast! I have more thoughts about this, but this is the gist of the answer to your question: because the goal isn't short queues, but rather faster total trips. |