If I can be so bold as to suggest that Beth was thinking we would figure out that building a character to top out between 20 and 30 would be a good thing. What I love about the game, is that there is so much freedom and so many options to screw it up - or make it awesomesauce.
I'd even go so far as to suggest that Beth was gently "tweaking the noses" of power players who focus on leveling. I think the leveling system in Oblivion works exactly as intended: it's supposed to help create characters who are slightly unbalanced, instead of the "jack-of-all-trades" you get when you "efficiently level." It's also supposed to get harder as you level up, and there is no "end game."
There's absolutely no reason you need to play this game to high levels.