Why, when U.S treasury yields rise, so do interest rates (on consumer and business loans)?

Consumer and commercial loan rates are made up of two components: the "risk-free" rate (the yield that you get from government-backed debt) and a "spread" that represents the risk of default, plus some profit margin for the lender. The higher the risk of default, the more the bank charges to loan money, to offset that risk.

So as government yields rise, so too does the "base" rate for these loans, and thus the overall rate goes up as well (assuming the risk of default does not change).

It's similar to how the price of applesauce rises when the price of apples goes up. The cost to process apples has not changed, so the producer just charges more for applesauce rather then reducing their profit margin.