This is how Pip manages its dependencies.
It will cache all versions to avoid downloading them in the future - Some people may or may not like this feature.
You can tell Pip to avoid using with the cache with the --no-cache-dir option. You can configure Pip so that it always ignores the cache with pip config set global.cache-dir false.
To delete previously cached items, if you have Pip 20.1 or newer, you can do pip cache purge.