One good and common example of why an SPG is good is on a liveaboard where you tank is filled and they want to look at your SPG to see all is well. AI-only is useless unless YOU are standing there.there is no reason to have an spg
I get it: you hate hoses. But an SPG can be a button gauge mounted directly on the first stage...so the tank filler can see it. And so can you, without firing up your computer.