If there is a reserve tank it is just another thing to go wrong, to be serviced and inspected etc.
Unfortunately the low fuel situation is normally learn't solo. This is due to the fact that most instructor s have been there done that and now are very careful about fuel required etc. In fact most I know would prefer to go over weight than have anything other than full tanks (this is training puddle hoppers not twins).
I had my scare in FL, which now I have more experence wasn't proberly as bad as I thought, but it did focus my mind on the fuel issues. And it was nice and easy in FL with a airfield every10 miles which sold fuel. (the handel jammed on the fuel tank selector on a PA28)
But it isn't uncommon enough that you see more fuel than the usable fuel getting put into a plane after a ppl hire has come back.(I have seen it 4 times in the last 2 years).
The only method i can think of,is if a Fuel supplier fills up with more than x amount for a given type they have to put a report in.
But that just generates more paper work which we have to pay for and smacks a bit of big brother. And its pretty easy to get round by only taking a half load.
MJ