I only started dating several men at once when I discovered FDS. I live in a big city so keeping a scrotation going on OLD is easy. The benefits are endless:
You get to compare men in real time. Talking to different men about the same things, like a situation at work, a hobby, a political issue, really opened my eyes to what possibilities there are. Like, I never realised it was an option that a man would be impressed by my creative hobby. I now know exactly what it looks like when someone actually thinks my job is interesting. My standards have evolved and gotten higher simply because I became aware of things I could expect in a man.
Rejecting men becomes so much easier because you can justify it to yourself by comparison. If you were only dating one man, you might hum and haw about whether he really is taking too long to reply or if him being boring really is so bad. When you have another one on the go who is better in that regard it becomes easy to block and delete.
Being rejected is also much less bad. When I have what I deem a great date and he doesn't text me, that quiet chat moves down the inbox incredibly fast and the next guy I meet reminds me that the other one wasn't so special. It becomes easy to let go of the fantasy in your head when you realise just how many men are out there and willing to date you. When you understand that there is no shortage, it's suddenly not so hard to let go of someone who obviously isn't into you and block and delete.
It jogs your memory. Which one's the one who never works from home, where does he live again, how many brothers are there?
So get out there are build a scrotation if you can! It has opened my eyes and helped me be emotionally stable while dating.