/usr/share/java is where (at least for RedHat/Fedora-style distros), the OS-supplied jars reside. Things like
jdbc drivers and stuff like that. You really don't want to dump
tomcat's internal jars in there. For one thing, they're not stuff you want to - ahem - "share".
I
have been known to go the other direction, however, and place a softlink(s) in TOMCAT_HOME/lib to one or more JDBC driver jars in /usr/share/java. Tomcat's OK with that.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.