As borne out by this thread, I'm sure there's as many reasons to sell (and buy) a gun as there are people and firearms. Really doesn't matter why, so long as both parties enter into the agreement of their own free will and are happy with the arrangement and its outcome. If there's ever a regret, the buyer will able to sell and the seller will be able to buy the same model down the road. It's a beautiful thing. Personally, no regrets regarding any guns sold and completely happy with my current stable. If and when interests change, see above.