Where, exactly, is the theft in renting the property?
Technically, copyright infringement isn't theft. Offering TV at a negative price to cable Internet subscribers is tying or dumping, not extortion. And in the same way, owner-absent short-term sublets are evasion of hotel tax, not theft. But morally, tax evasion could be thought of as like a theft from the other residents of the state, who have made a decision through their elected representatives to tax a particular behavior.
Joe Sixpack rents a place, but then he "has to cancel" and leave early *cough*. He pays the owner an "early-termination penalty", and then the owner would, of course, relist the room to be rented.
Where is the crime, and how would anyone prove that anything illegal had occurred?
The proof is that the property's owner failed to document good cause for early termination with more than three-fourths of the lease term remaining by five out of six sublessees of the same property. An allowance for "good cause" isn't a bright line, I'll grant, but it's like the difference between an excused absence from school in states with truancy laws and an unexcused absence.