Because rules say so.
https://www.lfs.net/agreement
As long as you don't have your own licence,sit patiently and quitly with "your friends account" and don't post stuff to which you have no legal access.
We're here in forums have read tons of "I use friend's/brother's/sister's/aunt's/grandfather's/Krusty the Clown's account". It does not matter who's account it is,as long as it's not yours,you should not come here with any claims. As simple as that.