That is because they do not understand that a runner is forced from a base, not to a base.
In other words, you don't have to go home, but you can't stay here. Wasn't that in a song?
The OP is discussing an issue made famous by the 1908 MLB incident known as Merkle's Boner. In that case, players were running off the field, and fans were running on it, thinking the game was over on a single to the outfield. But the runner at first neglected to run to second. It helped the Cubs win their most recent World Series, now 108 years ago. Maybe they'll win another here soon.
