Perhaps you are right, but it’s way more difficult, takes a lot of time and requires a different set of skills. If there is spyware in it, it would be illegal to remove it and distribute a patch for other users. So even if you find something, there is not much you can do about it.

It’s not very practical to add spyware into Libre Software though, because it wouldn’t be hard to find and it would be very easy for users to remove it.