My theory is the ratchets were 40 tooth or less, so the 12 point socket helped in tight situations. I grew up with Sears 12 point, 6 point were rare for me. Had a snipe on my 1/2" numerous times. The ratchet survived, some sockets didn't.12pt sockets are essential for 12pt bolt heads. You will need some for some cars etc. They work fine on clean uncorroded hardware.
In the past, 12 pts were included in basic sets, I believe, to facilitate the use of breaker bars. Breakers were essential because ratchets were rubbish. Today’s ratchets are as strong as breakers so the use of 12pt sockets to enhance accessibility is now obsolete.