A. What are you going to do? Let them shoplift whenever they like?
B. Assuming that's not an option, what's your second plan? Give them free counseling and rehabilitation at very high cost (a 30-day drug rehab costs $14,000 - $27,000; and what kind of rehab prevents shoplifting?), even though the recidivism rate for property crimes (like shoplifting) is 78.3%? Let them out on the street after wagging your finger, "please don't do that," only for them to do it again next week?
C. Assuming that's not an option... what option is there left but imprisonment of lengthier and lengthier sentences until the crime rate falls to reasonable levels?
Also, remember that shoplifting is not free. Stores raise prices to cover shoplifting losses, making shoplifting a theft against the community as a whole and not just the store. Stores also close when shoplifting gets too extreme, robbing the whole community of the store's services.
My position is strong law enforcement with stiff penalties; with strong external community programs to help people avoid feeling the need to shoplift, simultaneously. Not one or the other at the expense of the other.