Nobody, its not a matter of using people or flipping a coin. Its a matter of figuring out whats best for YOU. When you stop dating someone, it has to do with you deciding they aren’t quite right for YOU.
I know plenty of people who dated multiple people at the same time and it worked out fine. I also know plenty of people who dated, broke up and then re-dated (and got married). I think you are fooling yourself if you think people don’t compare dates, even if they took place in the past.
Dating has a large portion of learning about yourself in it. And sometimes, the way to learn about yourself is to reflect on how you interact with certain people.
I think if you are dating multiple people for a while (like a month) then that is wrong – you are asking people to invest too much emotionally. But the first few dates are more like interviews than anything else.
Did I ever date multiple people at once? No, but then again I married the only guy I ever dated. But it wasn’t a shidduch type system, so I am not sure that even counts.