This morning I had a better lather due to using more soap than I use with the Syntex. My theory now is that somehow the soap actually works as a detergent on natural hairs, thereby losing some of its lather creating capacity. The same you have when washing up: the amount of suds deminishes considerably with every greasy pan you clean.
@ Spendur: I have had a similar experience with much more expensive pure badger brushes as well.