I'd rather be more concerned with my browsing security than compatibility of one lonesome website; the website can be updated to become compatible with newer browsers. :PI bet it's locked at IE 9 because some important web page app doesn't work in anything above IE 9. We only upgraded from IE 8 to IE 10 company-wide at my work in September because some web page applications use a web browser and only worked in IE 8 or older.
What I don't get though is why the library computers at said campus of my college are only running IE 9, whereas (at least) two other campuses within the college have both IE 9 and Firefox.