From my experience it is more of a practical limit then anything else in older versions. Access starts to get flaky before you reach the size limit.
I suspect though, that in Access versions after Access 97 it's more of an artifical limit. After 97 they threw out the old DB engine and stuck a cut down SQL Sever engine in there. I don't have any real experience with anything after Access 97 to say how much more powerful it is though.
Jay