Lockpicking is a useful skill. You will need Lockpick level 4 to get one of the Tresure maps for instance. Also some of the locked chests have very high value items in them and some need Lockpick level 4 or 5 to open.
One thing I do when I come across a locked chest that I cannot open (before getting high level lockpick) is I move it to either Ars Magica (my home base) or some other central location in the area that I am in. Then I come back later and open them all when my skill is high enough.
Be aware that most locked doors in dungeons cannot be opened even with Lockpick level 5. You need to find the levers that open them.
