The purpose is, for most people, to know when a charge is made that they didn't cause, a fraudulent charge, a theft.
It's important to know if someone is stealing money from your account. It's not nearly as important to be reminded of something you did within the last hour or 48 hours and you know you did.
Imagine my surprise when I learned today that they don't always notify you. It depends on "how the merchant presents himself". If he presents himself as having been paid online, by phone, or by mail, an alert is emailed (or texted) to the owner of the bank account.
If he presents himself as a store, a place one can go to in person, and pay at the cashier, presenting the physical card, then they don't alert you, because after all, you were there and you already know about it. BUT YOU DON'T HAVE TO BE A STORE to present yourself as a store.
I learned this only by accident today. Last Thursday night I bought three things, a used DVD for 7 dollars and a bathroom rack for $49.50 from separate Amazon-related dealers, but not sold or shipped by Amazon. And a $20 remote control for my TV, on Ebay.
For another reason, a story in itself, I got no confirmations of purchase and no receipts. Sunday, I checked on Amazon and both items had already shipped!**** Without my paying them, it seemed!!! Amazing. But I checked on the bank webpage and they had been paid. But I got no alerts. ****I got the DVD on Saturday, the remote on Monday, and the rack on Tuesday.
So I complained on Sunday. She filed a report. Today a nice man called and he explained that if a store sent in a charge, they didn't alert me, and afaict apparently any place can pretend to be a store.
He agreed with that.
But what about Ebay. Just last October, I got an alert when I charge $20 to Paypal, to pay ebay. So Paypal is not a store. Why didn't I get an alert this time. He said that when I pay Paypal, I'm not really paying them, they're just an intermediate, and I'm paying the actual vendor, and if he says he's a store, he's a store, even afaict if his address is a secret and no customer has ever been there.
I told him there was a big hole in his procedure and that they give the impression they will notify customers of every online purchase and they will eventually be sued big time when someone loses money. He said he'd put a report in to... I forget what he called them, or it.
So there you go.
And what good is it to be notified, alerted, if you can't count on always being notified? You can bet your bottom dollar that thieves will pretend to be stores. So only the honest places are causing me to be notified. I don't need these emails because if I ever needed one, better evidence would be my bank's statement or an image of my online bank statement. I've been wasting my time reading these alerts and changing the subject line to say exactly what they are for.