I hate to admit it, but the LHS owner is probably right. He could stock an assortment of 50 different kits, but will likely only sell a few within 6 months.
My observation, through 40 years in this hobby, is that us aero-modelers are a cranky bunch. The LHS could stock a 60" Corsair, but we won't buy it, because we want a 65" that would better fit some 25 year old engine we have. He could stock a bubble P-47, but no, we want a razorback instead. The variations of kits are endless, and so are our excuses for wanting something that he doesn't have. We'd end up complaining that he isn't stocking the exact kits that I and only I want. And on top of that... we're a bunch of tightwads. He could put a price of $200 on a kit, but no, we won't pay a dime over $180 for a "box of sticks" and walk away.
Yes, my examples above are facetious & silly, but if we're honest with ourselves, we (the collective of builders) can see that grain of truth.
I'm off my box now, too!