So how does Google - or any other search engine - know what your bounce rate is? How could they possibly measure it? At best, they could only know about traffic coming directly from their own pages, and even then, how do they know which other pages on your site have or have not been visited?
Also, as explained above, a high bounce rate does not necessarily indicate visitor dissatisfaction. Bounce rate needs to be read in conjunction with other information which, again, search engines do not have access to. It would therefore be an unreliable metric to use in ranking, even supposing they could measure it.