Why can't install lxml with pip?

Install pip first:

opkg install python3-pip

Install lxml:

root@GL-A1300:~# pip install lxml

Collecting lxml
  Using cached lxml-4.9.3.tar.gz (3.6 MB)
  error: subprocess-exited-with-error
  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> See above for output.
  note: This error originates from a subprocess, and is likely not a problem with pip.
  Preparing metadata (setup.py) ... error
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

Why can’t install lxml with pip?