Well, I can think of at least one good reason to do it in my case: keeping rinsed yeast in mason jars won't smell up the mini fridge in which I store my yeast. My current practice involves just collecting the slurry in a one gallon plastic bag. This gets messy when pitching to a starter and it really starts to smell after a while.
So your still making a starter? with saved yeast no less? < giggling >
My simple method is make a 1.5L starter and save a couple whitelab tubes (or 4-5 tubes when making a yeast blend). Each tube is pure as possible unlike `washed slurry' , so when I need to make a new starter I just pitch a tube.
Rinsed slurry- unknown level of possible contamination
Saved starter tube- very low level of possible contamination
Ease of rinsed slurry- carefully collect slurry > rinse> make starter> pitch
Ease of tube- > make starter> pitch