It was needed. Just the trade off wasnt worth it.
it wasn't needed -- need means "must have"
they're a fantastically popular franchise with a ton of money... and did it without the optimizations.
if they never did these optimizations they'd still have a hugely popular, industry leading game
minor tweaks to weapon damage will do more to harm their bottom line compared to any backend optimization
I'd argue it was incompetence.
It was wanted and intentionally selected, but it wasn't needed.