[monocasa]

It does, but major part of flash encryption is to protect your supply chain. Ie. to keep people from cloning your boards and just dumping your software on them. It's also a bit of security through obscurity (which despite the memes can be an important piece of defense in depth) to make the MCUs a bit more difficult to attack if you don't know the code that's running.

[XorNot]

Except an attacker operating at that scale would just start decapping the chips and inspecting them.

[monocasa]

Decapping and dynamically instrumenting a chip with little pins like you'd need to do is a lot harder than a timing/glitch attack.