Sorry, simple foul tip question

[cpa]

There is every reason in the world to give a foul tip signal on a caught ball -- especially if you have base runners stealing or just off base when it occurs. A foul tip imposes no tag up responsibilities on a runner, whereas a foul ball caught by the catcher (anything OTHER than a foul tip -- backwards line drive, pop up, whatever) imposes tag up responsibilities

Given that a strike call and an out call can look similar, the foul tip signal communicates that the ball is live and that no tag up responsibility exists.