Many of the high street shops over here don't have the budget for expensive tag based alarm systems or CCTV surveillance which incidentally I've always thought of as primarily a deterrent rather than a crimestopper. However they still have a need to protect their good from small time robberies and opportunist thieves.
One of the systems they use is simply to build a seat on top of a step ladder and put a security guard on top. From that vantage point he can usually see the whole shop and helps makes sure nobody makes off with their goods without paying. Plus, due to low labour costs it is much cheaper to implement than tags or CCTV. Here's an example:
Presumably if he spots something there is someone else to stop the thief getting away because I don’t see safe way of getting down the ladder very quickly. In any case this is quite common not only in shops but also in car parks where you get more sophisticated turrets from which security guards have an aerial vantage point over the parking lot. If it’s used so much, I guess it's because it works.