I came across an interesting study done by David Durian at Ohio State:

Getting [ʃ]tronger Every Day?: More on Urbanization and the Socio-geographic Diffusion of (str) in Columbus, OH.

http://repository.upenn.edu/cgi/viewcontent.cgi?article=1004&context=pwpl

I also cringe when I hear this pronunciation. The article helped me better understand its origin. However, even knowing how this came to be doesn't negate my distaste for the pronunciation! Don't even get me started on "try and" vs. "try to"!