In a business context, it usually happens that hardware is cheaper than software (licensing) which is cheaper than engineering labor. Tack on the opportunity cost of delaying business advances/features and it's usually cheaper to just throw hardware at it.

There's a tipping point where you have so much hardware there's big savings with optimization. Things like Postgres and the Linux kernel have a lot of optimization put into them and there's an insane amount of hardware out running that code.

That said, slow software sucks.