Public executions were partly entertainment but partly "hey, don't do this or you'll end up like so and so"

Fun fact: The last public execution in the United States was in 1936, when Rainey Bethea was hanged in Owensboro, Kentucky ... 20 000 people turned up to watch. Public executions are a daily occurance in Islamic countries

Why did we stop having public executions in the United States? Just curious.

Out of control crowds ?