according to the Obiwan books....if a padawan has not been chosen to be an apprentice by the time he/she turns 13 he/ she goes on to the agriculture corps....they use the force to help other societies flourish under harsh conditions.
As for there being force sensitives running around unchecked...well there are the witches of Dathomir and
others...usu they are the "prophets" of their villiages...the wise ones...
yeah...just look at what the students of Luke did before they were found. They were the 'prophets', or they survived in the mines of Kessel, or they were witches...and on and on...although, most of the time, if they aren't trained by the Jedi, they aren't trained at all...so it really isn't that harmful to society to allow them to not be trained.