Shopping has always been a tiny rush of happiness in many peoples' lives. I think free shipping only makes this rush more convenient, accessible, and addicting.
And also with electronics, why should I go to the store if I receive the package the next day?
With B&M shopping, even if you know exactly what you want, you have no idea if it's actually in-stock at your local $store. So you drive there (wasting gas and a lot of time), wander around inside looking for it, only to find it's not even there! Then you have to go drive somewhere else hoping they have it, or get someone there to look it up and see what other store does have it, etc. All in all, this can waste a huge amount of time and fuel just to go find one single item.
With online shopping, it's right there on the website: you can see everything the shop has to offer in one place, and you can see if it's in stock or not. If it is, you click "buy" and it shows up at your doorstep. If it isn't, or there's some problem, that might mean a delay in getting your item, but you're not going to waste a lot of time and energy running around in the process.
Many stores, especially the chains, have webpages that tell if an item is available in a store or not.
Amazon uses fast shipping, but they won't guarantee when it ships. I've been burned more than once (I mostly quit using them a couple years ago) because the thing I wanted didn't ship in time.
I've seen online shipping speeds get a lot faster over the past couple of years so if you have quit than you might be surprised at speed and value if you come back.
And as the other responder said, those inventory counts might not be accurate; if there's only one in stock, and someone just bought it 10 minutes ago, is the webpage really updated that fast?
I did grow up in relative poverty, though not in a housing project. The area I grew up in, at the time, had lots of Crack but no Meth/Heroin etc. Still, never heard of it.
I'm quite sure it's an urban myth :-)