I make it a point to scan my junk mail just in case something goes in there that shouldn't.
I've gotten in the habit of doing it quite fast, but was fortunate that I didn't do it so fast that I missed seeing I had a genuine email to tell me a large rebate had been approved.
The rebate in question had to be claimed electronically. I had to choose whether I wanted a virtual Visa gift card or a physical one.
Now, in my case I wouldn't have forgotten this rebate even if I had missed the email because I create tasks / reminders for things like this precisely because they are easy to forget.
But it still goes to show that it's worth checking junk mail carefully.