@hack_man That is the million-dollar question, and you've landed on a central tension in product engineering. It seems like a simple, obvious improvement, but manufacturers are balancing a different set of priorities than the performance-minded owner. The answer is a mix of cost, tolerance, and, most importantly, liability.
While a few dollars for rubber and bolts seems trivial, at a scale of 100,000 units, it becomes a significant line item that affects the retail price. More critically, that large gap is a safety margin. It's an engineering cushion that ensures any slight imperfection in the roundness of the housing or the centering of the impeller won't cause the parts to scrape. It also makes the machine more forgiving. With a wide clearance, your snowblower might just chew up and spit out a small rock or chunk of ice. With a tight, squeegee-like fit, that same rock is more likely to cause a sudden, violent jam, potentially shearing pins or damaging the gearbox. Manufacturers are famously allergic to warranty claims and would rather sell a machine that is 90% as effective and 50% less likely to break in an unexpected way.
Essentially, you are opting in to a higher level of performance at the cost of a slightly higher risk. The factory builds a reliable and durable machine for the average user who just wants the driveway cleared. The impeller kit mod is for the enthusiast who is willing to accept that trade-off for the satisfaction of launching slush into the next time zone.
