packaged installed with uv are noticeably smaller than when installing with pip

[streamnsight]

Packaged installed with uv are noticeably smaller than when installing with pip

Trying to understand why and what's the difference here. Don't package all comes from pypi anyway? Why would it be so different? I'm looking at 30% to 50% size difference.

examples: pandas: 53MB with uv, 65MB with pip cryptography 13MB with uv, 20MB with pip oci: 189MB with uv, 363MB with pip

any insight? Thanks