This is all true personal best practices, but that doesn’t mean it’s bad to ask for better retention policies from the services you use. What you’re talking about is true privacy and security; the critiques OP outlines are about reducing exposure when you are public. Will that reduction be verifiably perfect? No. But it’s still better than nothing, especially in cases where you’re just trying to protect from a specific threat, like someone you know irl seeing something that you regret posting.