Because Bosch's claims are backed by engineering realities the others can't match. Its motor is only 525 watts. Universal's motor is 1.33 times stronger than their best. Our mass-marketing competitors build transmissions with inexpensive spur gears. The first shortcoming of spur gears is that they break under stress.
Stress is a bowl full of whole grain dough or a triple batch of oatmeal chocolate chip cookies.
Things you need your mixer to handle. Buyers comment daily that they're getting a Bosch now because their other mixer, often brand new, failed. The second major problem with spur gears is that even before they break, they transmit torque poorly. The Universal's competition starts with a much smaller motor, then spends a big share of it on friction. Which is why many big mixers have surprisingly little oomph .