I'm happy to buy in short occasionally for three possible reasons:
  • There are hyper aggressive taz types that I can't read yet, and I know I could lose a couple buy-ins working out the read.

    There are some "any two" players that successfully play based on Implied Odds, and when I buy in with one of the largest stacks at the table, my AA becomes an instant target for unreadable shenanigans.

    When I moved up stakes, I don't want to play with scared money, or I might be pushed off a hand because of my stack at risk, rather than the strength (or relative weakness) of my hand. A short stack helps me keep mental control.