I use ice in bourbon maybe twice a year. Tonight was one of those times since it is very hot here. I find ice brings out certain qualities in bourbon and in particular it accentuates the rye character.
This may be a previously unheralded reason for the decline of rye whiskey and the amount of rye in bourbon mashbills.
In the old days before ice, rye fit in well to the light corn, wood gums and tannin frame of whiskey.
The more ice became used, especially after WW II, the more the rye elements obtruded and seemed out of place (not to me, I like rye, but to many bourbon and rye buyers as a whole).
The renaissance of rye in whiskey can be laid I think, in part anyway, to the tendency of the main whiskey writers and their acolytes to drink whiskey neat.