Leveling up legerdemain is a boring grind involving a couple of weeks of stealing and laundering. Lockpicking also levels it. Being able level your legerdemain on a practice chest would still require effort and time spent, but without the artificial restriction of daily laundering/fencing limits. Like DPS practice dummies, this would be an easy way to add functional value to housing.
It would also have RP value for players and guilds full of dirty criminals -- I mean, players devoted to relieving people of useless extra possessions. Of course a guild focused on thieving would want a training room! (They'd probably like a pick-pocket dummy, too.)