The other side of that coin is that the few businesses who actually do keep good inventory do exceptionally well. I’m talking specifically about Lowe’s and Home Depot. I absolutely love, as a consumer, that I can go and look on their site/app and see that there are X items at Aisle Y Bin Z and it’s almost always perfectly right +- a couple of count. These brick and mortars prove it’s definitely possible to offer that service even if you’re a huge big box store.

There are so many places that are the polar opposite as you imply. One particular annoyance I dealt with recently is Tractor Supply Co. Their online inventory is wrong enough that it can never be trusted - if you don’t want to waste time on a trip to the store you have to call them beforehand to see if an item that is ostensibly “in stock” online is actually in stock.