In a business environment, yep for sure, and as already said once you've been doing it for so long, it's a hard habit to break.
I do it now, out of habit, but more so to get a gauge on how far I can go on a tank, as fuel supply at the time of need isn't always guaranteed.
I once told of a story where I drove out to Wilpena area, assuming that fuel will be available at any time, but it wasn't to be.
The drive from Renmark to Pt Augusta late at night(between 9ish and 1am(ish) was slow as I expected some fuel stations to be open till later, hopefully at Burra, or at least Orroroo.
But nup!. My Rodeo at the time was very unhealthy and used much more fuel than when it was in better condition, and my driving habits are such that I always drive overnight.
So to stop and wait for a petrol station to open wasn't an option I considered(for that drive).
In the end, I just drove all the way to Pt Augusta at about 40k/h in as high gear as I could, and made it .. just. Filled up and kept going up to the Wilpena area as I planned, just a few hours later than I thought I would be.
No problem, still had a nice drive.
So for me, keeping an eye on fuel use and economy isn't about 'the money'. If it were, I wouldn't be wasting $s on fuel for frivolous drives to no mans land for no reason ... it's just that I can!!
Also keeping a track of fuel usage over time does reveal a bit of an insight on the health of the car/engine, as it wears and uses more as time goes by.
Over the past 3 or so decades the only cost metric I had in my spreadsheet(s) was cost of fuel per klm taking into account fuel cost(and type) and klms done.
It was always a hard choice to decide to go with an LPG system over a diesel vehicle for (courier) work. LPG was usually the cheapest(ie. back to the tax time reasoning).
As a business, the cost of fuel was important, obviously lower was better. Now, using the same spreadsheet template, I don't need to keep track of this .. but as said before habit is hard to break, and I couldn't be stuffed editing the spreadsheet either! [biggrin]

