please don't accuse shops of trying to cheat you if their standard practice is to tear fabric instead of cutting.
(1) some people consider tearing to be a more accurate way of getting sections that are on the straight of grain at both ends. it's a more reliable way to ensure you have the same number of usable inches all the way across the WOF. i recently bought a sustantial stack of yardage from a very nice shop. when torn, the fabs looked a bit wonky. once washed, they came out of the dryer so nicely rectangular you'd have thought they were cut by a machine.
(2) in the shop i used in my example, the owner tore generously, which means she added at least one extra inch, just in case, to each piece i bought. i suspect that most shops that tear do the same.
(3) it's faster than cutting. at the Houston Quilt Festival two years ago, one world famous and highly respected shop was selling nearly all their fabs at a deeeeeeeeep discount. naturally, the lines were very long and their booth was very crowded. they tore everything unless a customer specifically asked them not to. i literally bought a suitcase full. not a short cut in the bunch.
cut vs. tear is a personal preference. the choice has nothing at all to do with honesty vs. deception or laziness.
all you have to do is state your preference at the table. too easy.