It was easy to look at statements when they arrived by mail.
But with paperless billing, you've got to conscientiously log into your credit card site each month. If you have four cards, that's four logins. Who's going to do that? Not many.
The only reason I review my transactions it's because it's easy through an aggregator like Monarch (was using Mint before it shut down). And the only reason I do that is for budgeting -- reviewing transactions is just a side effect.
It still annoys me to no end that I don't have a single bank or credit card that will attach my statement as a PDF to a monthly email. As long as there's a secure email transmission connection, I don't understand why they won't do that.