"So the question I ask is, what’s the point of all this? What is the threat of a tourist travelling to a holiday spot? "
if you employ people to do basically boring jobs on low salaries they will find a way to make it more interesting - thus policemen will drive at ridiculous speeds to arrive at any possible "incident" (especially if they think there might be a fight) and 4 cars arrive together, ambulance crews will drag you to hospital even if you're capable of walking, Border Force will make peoples life "interesting", Security will examine EVERY bag to wind people up.
It's human nature