If you're running a compute task that is slow and takes an hour, then 5% additional speed saves you 3 minutes. If the computer gets 2x faster, then an additiona

If you're running a compute task that is slow and takes an hour, then 5% additional speed saves you 3 minutes. If the computer gets 2x faster, then an additional 5% improvement only saves you 1.5 minutes. So if utility is proportional to time (and hence inversely proportional to speed), then this makes sense.