Reason for deprecating a rule

“Why is this an issue?” popups will say “this rule is deprecated” (or will soon be deprecated) but don’t always give a reason. Sometimes it’s clear (e.g., “use rule XXX instead” which implies XXX is better) but sometimes there’s no way to know why. Is it because industry best practices have changed, or because the feature is obsolete (so up-to-date code wouldn’t be triggering it anyway), or what? It would be nice to see a rationale when the popup tells me the rule is/will be deprecated.