I have experienced this as well but I have no idea why it is. I dry fired a P2000 (as well as a P2000sk, P30, and P30sk) last weekend and found them all to have smoother DA trigger pulls than both of my usp compacts. I can’t judge whether the pulls are lighter but they were definitely smoother.
If the usp is the older design (as compared to P series or others), with different internals then maybe that contributes to the pull.
The Match trigger kit helps with the usp compacts.