It would definitely make the engine implementation more simple and elegant, but why exactly would that be worth it? Why would that be worth all the downsides?

It would definitely make the engine implementation more simple and elegant, but why exactly would that be worth it? Why would that be worth all the downsides? I think a good analogy, say that I'm implementing a database. In my database, every single time it handles a query, it always does O(n) search across every record to find matches. The implementation would be so simple and elegant!