1. Panels are fixed in place and don't have title bars etc. They're the only window type like that so you'd have to go to extra effort to make a UI to "lock" windows and unlock them or whatever.

2. If you delete the launcher then how do users start apps? Some old DEs let you right click the desktop but that's not very discoverable.

Much easier just to have settings somewhere do let you say which side (if any) you want panels on.