Why do most programs separate Find and Replace dialogs? Obviously, I'm talking about apps like text editors and word processors, apps that are used for editing content.
It just seems strange, at best, to completely separate functions that are basically two sides of the same coin, and can get downright frustrating when they're implemented as separate windows instead of tabs in the same window and you decide to replace some of the already found matches.
From the interface design perspective, I don't see how the inclusion of another text box and two more buttons required for Replace (all other options are usually the same for both Find and Replace) causes such a clutter in the interface and cognitive overload that it requires a basic Find version for "non-power users".
The only program I can think of that combines these two is TextEdit. (Ironically, there's a question on Apple StackExchange about where the Replace function is hiding in TextEdit, but that's because it's named just "Find" instead of something sensible like "Find or Replace".)