Probably because your assumption is wrong - they host a live shell and documentation search.
https://web.archive.org/web/20260220092649/https://pandas.py...
https://web.archive.org/web/20260225185816/https://pandas.py...
(I don't know anything about pandas, incidentaly, I just did some basic research before posting.)
That's not a shell, it's a Python interpreter compiled to WASM and running in the browser.