I certainly used to buy them as a student. Mainly a return if there was a required unit out. I would nip out and back and come home!That might be useful if you had a TOC specific Advance that only got you to Picc and were going to the university or around there. I've certainly bought a non-zero number of that ticket when I was at uni.
Bayswater to Queensway via Notting Hill Gate looks a reasonable route on the tube map, but not on the ground.Two on London Underground..
I understand that a number of foreign visitors buy a £4.50 single to go on the Piccadilly Line from Covent Garden to Leicester Square a distance of less than quarter of a mile or 5 minutes walk.
Embankment to Charing Cross is also 5 minutes walk along Villiers Street.
There isn't a specific fare for that journey - it is just offering a generic single to Zones 1-2, which could be used to travel to St Pancras, but is also valid for many more useful journeys.London King's Cross to St. Pancras International via Finsbury Park - £6.50 single/£4.30 Railcard single
Whilst that's a steep fare for a distance walkable in 10 minutes (if you know where you're going), it would not be true to say it's totally pointless. There are even circumstances in which Oxford Road to Deansgate would not be a pointless journey (though I admit it would make little sense to pay for it specifically).
Those short journeys seem to confuse NRES.
Birmingham New St to Birmingham Moor Street gives two options; walk ( no fare) or walk to Snow Hill (further, I think than to Moor St) and catch a train from there.