The reason is that mono leader is less visible than braided line but I don't think ling care if a guy has nylon rope tied to your lure but however in my opinion I have found the problem with braided line is it absorbs water and pulls it up through the eyelets of your pole and freezes your eyelets and reel.
I use flouro leaders on my braid because as said it's way less visible.
Most of the braids are bad for icing up.
The best I have found so far though is Tuff Line Duracast. It is a coated line that doesn't absorb water.
In fact it handles and works as well as mono which is great.
I use 15 and 25 pound and it gets a wee bit wirey in the cold but no worse than any mono and it's nice and thin with zero stretch.
I connect flouro or mono leaders to my braid with a back to back uni knot.