I'm with you on this. For my very first lager, I was really concerned about underpitching. Fortunately, I had a friend working at a brewery bring me about a half cup of creamy white, pure, active lager yeast (S-189) taken from a primary. I stepped it up with a fresh half gallon of wort before pitching. I didn't oxygenate at all beside the usual carboy shaking, and yet I had a full krausen formed on that beer when I awoke 6 hours after pitching.
The problem is that it's just kinda hard to always grow up yeast cultures that big. There's room for infection and error every time you touch yeast (from washing & collecting, to making starters & stepping them up). Its simpler for me to pitch my standard 2 Packets of W-34/70 into my lagers now.
But yeah, I agree with you. If you can consistently build up massive slurries, then you can find other things to worry about besides oxygen.