I understand why a person might opt to think in that way! It's an obvious approach when people fully trust every part of their systems. It's perhaps possible

I understand why a person might opt to think in that way! It's an obvious approach when people fully trust every part of their systems. It's perhaps possible some might differ, especially in a context where limiting trust and misuse-resistance are concerns. Giving people the choice of encrypting or signing or both could seen by some as potentially less than maximally misuse-resistant.