Your game works. You've tested it extensively. But on launch day, what decides whether a player actually gets in isn't just your code, it's whether they can buy and access it.
That moment lives on someone else's storefront – Steam, PlayStation Store, Xbox, the Nintendo eShop – through regional payment methods that are largely out of your control. When everything works, nobody notices. And when it doesn't, players notice immediately.
Retail checks validate that full sequence, from purchase to download to the moment gameplay begins, making sure players get what they paid for.