Our first 5th wheel came with one...never bothered to use it.
Pretty much every 1/2ton or larger truck comes with a receiver hitch that can move a travel trailer with just a $25 ball (may not tow well but it can be done). Makes it very easy for thieves wanting to get into the game.
Most trucks need to be set up for a 5th wheel hitch at significant cost. Then they need a 5th wheel hitch which starts at around $500. Unless they are specializing in stealing 5th wheels, it's just not worth the hassle.