One feature I really like about my Discover card is the cash-over feature. For those not familiar with this, this allows you to get cash with a purchase at certain stores (typically, grocery stores) but it is treated like a purchase instead of a cash advance. So you can have a small loan with a grace period or just a way to access cash without having to rely on a bank stop or a debit card. The only purchase I've made so far in Q3 on Discover was for cash-over.
Sam's Club and Walmart cards have this feature, too, so if you have one of those (or just don't need that feature), this might not be a compelling enough reason to keep the card. As has been stated, credit is unique. What works for you won't work for others always, and vice versa.