A) The folks back home just wouldn't understand why a former football star wants to hang drapes for a living.
B) You don't want your friends coming to you for free advice about their paint color choices.
In Connecticut, Nevada, Oklahoma, and several other states, calling yourself an "interior designer" means the answer could be (C) if you lack the years of post-secondary education the state requires. I blogged about the Institute for Justice's anti-interior design cartel jihad earlier this month. For more info, check out the study they just released on the "dangers" of unlicensed interior designers.