John Lydon won't do adverts for clothes shops. It's a matter of integrity, you see:
"There's a thin line between self-parody and ridicule."
Apparently, advertising clothes is ridicule, which is wrong, whereas pocketing the money from Schiltz for those beer ads was self-parody, which is fine. We imagine the fine detail of where that line lays is down to how large the cheques are.