What advantages do libraries offer over the internet for doing a literature survey in Mathematics or CS Currently my literature surveys do not involve trips to the library and I am wondering if I am missing out on something important. What sort of material/knowledge can the library provide that I would miss on google scholar. 
Thanks
Almost none.

I recently wrote a research survey, while on sabbatical at an institution without a physical library, but with extensive electronic subscriptions.

I never missed having physical library access, even for papers dating back to the 1840s.  (In fact, the historical literature was more likely to be freely available than papers from the 1980s.)  Occasionally I had to use my home university's VPN to get access to a different subset of the electronic literature, and there were one or two books that I had to download via bittor—sorry, that I had to borrow from colleagues down the hall.  Yeah, that's it.