Good heavens, I’ve been using a wallet case (albeit a ‘folding’ model) with my iPhone for ages!
I’m one of those who prefer a small enough phone to fit into my pocket, and with a wallet case, I can hop on my trike (with a big basket in the back for errands and grocery shopping, for example) with all that I need – driver license (in a see-through slot), (medical) insurance card, CC and debit cards, some cash, my business card, even an RFID-blocking card from SignalVault.
In fact, both my elderly parents have them, too, which contain their Medicare and Medicare Supplement cards in addition to photo ID/DL, credit/debit card and cash. A godsend especially for mom, who otherwise would have to look for all those items in her, uh, pocketbook/handbag – always a nightmare either at the doctor’s office or at the check-out 
And since everything is kept inside the (folding) wallet case, there’s no risk of anything getting damaged on the outside.
Moreover, since I’m esthetically ‘conscious’, I even have matching cases for my other iDevices – or iToys as my mother calls them!
Finally, since I travel mostly overseas, I use the SD slot in my (also RFID-blocking) passport case for the SIM tool and other SIM cards. Somehow that makes me feel a little easier than having the SIM cards with the phone…