Gotta argue this one really, not in defence of Tesla but in criticism of every other maker.
Most of those cheap "attached with bits of string" shelves end up blocking the interior light, don't fold and have no-where to go if you need to remove them for a load.
Mercedes A class gen one had roll cover - it rattled dreadfully not fitting for a Mercedes - this was replaced with a hard cover on strings in the refresh - this rattled and squeaked dreadfully.
Chevy Volt/Vauxhall Ampera had a cover - a stretchy handkerchief attached with bungy cords to hooks in the boot, at least this was quiet and fitted round odd sized loads
I've never come across the "perfect" load cover over forty odd cars