Funny you mention this, because I just managed to somehow lose one of two feminized Cheese seeds I was soaking in a paper towel. I get impatient waiting for them to germ, so I was unfolding the towel to scope them out and must have dropped one on the ground. I felt like kicking myself in the nuts for being such a doofus. I'm lucky the other seed did germinate and is now in a peat pellet.
But anyway, as to your "why" question, in my case it's partly due to stinginess. I have peat pellets and other stuff that I could just poke seeds into and walk away, but if a seed isn't going to germ I don't want to "waste" a peat pellet on it. So I often end up soaking seeds overnight in a glass of water, waiting for a root to show before I put them in solid medium like maybe vermiculite or a peat pellet.
I guess my reasoning is that if I put a seed in a peat pellet or just a little cup with dirt in it, water it, and a week later there's still no signs of germination, how do I know what went wrong? I'd have to tear the peat pellet apart and see if the seed ever sprouted a root. I guess I'd rather know that before I put the seed somewhere it can't be observed directly.