why does gpg –recv-keys strip 3rd party signatures?

When I download a key from keyserver.ubuntu.com from the keyserver web ui, that key includes 3rd party signatures.

key=0xa9a14f22f57da182
curl -o key.txt "https://keyserver.ubuntu.com/pks/lookup?op=get&search=$key"

key.txt does include 3rd party signatures.

If I instead do this:

gpg --keyserver keyserver.ubuntu.com --recv-keys $key

no 3rd party signatures are imported.