Although that number does seem high, it isn't really alarming. It is because of the way programs are written for Linux as opposed to other OS's. In Linux many programs are really just a bunch of other programs that all do a small function, but can be collaborated into one larger program. This is why we have dependencies. The reasoning for this is because in open source software, the ethos is "do one thing and do it well". When programs are written to do one thing and do it well, another programmer doesn't need to write that part of his program, because someone already did that, and they can just piggyback off of that program for that particular function.

I recommend keeping your PC up-to-date because most of the times the updates are bug-fixes, feature enhancements or security fixes. I personally run updates whenever the default schedule is (I think it checks once a week) and notifies me to run updates.