I'm with baudib, you're definitely undervaluing AK and should be more apt to get your chips in pre, especially with initiative.
When it comes to open shoving, or shoving over a raise, you have to combine fold equity with pot equity to get your true equity situation. Since AK is a coinflip against any pocket pair less than KK, that's ~50% pot equity before FE is even added to the mix, meaning your total equity is going to be >50% if you're the one shoving AK preflop and there's any FE to be had. Who wouldn't shove with those odds almost every single time?
That's not to say it's always a snap call against TWO all-ins, but it all depends on player images, stack sizes, blinds, etc. In most situations I will have to call one all-in pre with AK, and in nearly every case where I think I have even a little fold equity by over shoving, then I'm doing so.
Assuming a shove is always a PP is definitely a bad assumption. Any player that picks up on this would totally exploit you.
Pocket pairs constitute less than a 6% range. That's a very small part of most people's shoving range, especially as stacks decline. And only very bad players (or maybe higher level thinkers exploiting lower level thinkers, but that's less common at the smaller stakes) will open shove AA/KK for more than 10-15bbs. If they're making a huge overbet shove, then odds are it's a smaller PP or big suited cards (not counting total bluffs, which will make up some percent of most people's range as well), so AK has good equity against that overall range.
Also, using "average stack" as your benchmark is flawed, because it's meaningless out of context. Average stack on a final table can be a very short "ATC" shoving range. And the larger the stacks involved, the larger the fold equity, which has to be considered.
Now the story may be different if you play DONs or Satellites and are on the bubble with a guaranteed 1st prize stack. It's not uncommon to fold even KK here, some even claim to fold AA (although I can't say I've ever done so), unless you have the monster stack and can afford to fold to a shove that would threaten your finish. But in a regular game, I'm rarely hesitating to do the shoving with AK.
AK is a donkey's favorite hand. AK is also overrated as hell. If the flop doesn't hit u 'str8 draw, one or two pair, or a flush draw' just fold fold fold fold......fold.....
Perhaps post-flop, but we're talking pre-flop shoving here. Post-flop is an entirely different ballgame, and it shouldn't be difficult to fold even AA/KK in specific post-flop scenarios, let alone AK. Put it this way: I can more easily fold AA/KK post-flop than I can fold AK pre-flop.