Earlier quoted context omitted.
As explained in the article a lot of people use the iCloud mail for their apple account and they don’t check it because they use another provider main mail address. Furthermore if they contact them from their email for support they have no way to associate it with the mail registered in the system, so they can’t help them. If you ask me they seem both very valid points.
Do you have a number for “a lot of people”? I am very skeptical of this data point. This email address is used for a lot of communication with Apple, e.g. receipts from App Store.
I bought my iMac on the Apple store, and the receipt was also sent to my personal account.