I have a few wallets with alleged RFID blocking. For those its mainly to stop arse grabbing attacks where card info (or security badge info) could be cloned with a little badge reader held in someone's palm.
You'd also be surprised how powerful smart cards are these days. the aforementioned NXP chip has 586 KB ROM, 144 KB EEPROM and 11 KB RAM, crypto coprocessors for RSA/ECC/DES/AES, and a 32-bit CPU.