Because then he wouldn't own the land and thus would no longer be legally liable. See, he is offering the land for $30K, not just the removal of the fence. From the articele:
The speculator, 44-year-old Don Connolly of Valrico, now is offering to sell the land behind each of the homes for $30,000 per homeowner.
If I were a homeowner I'd be sure to contact the local asessors office to make sure the new owner was being asessed properly for each $30,000 section.
I'm guessing his asking price would drop quickly.