Business incentives. It's a classic incentive tension between more time on nicer code that does the same thing or building more features. Code expands to it's performance budget and all.

At least on backend you can quantify the cost fairly easily. If you bring it up to your business people they will notice easy win and then push the devs to make more efficient code.

If it's a small $$ difference although, the devs are probably prioritizing correctly.