Because part of poker is being smart about making a profit. And going bust on the bubble leaves you with nothing, while sometimes making a big laydown is the difference between getting paid or not. Sometimes, it's best to lay it down and let someone else make that mistake.
folding is not the most profitable option, though. it is the safest to guarantee a cash on the bubble but, if you're thinking about long term profit, you need to call in this spot.
for simplicity, vs a 100% range, qq is an ~80% favorite. so, you can say that 1/4 times, you bust and 3/4 times, you double up to ~20+ bbs.
so, you can either have a 4/4 chance of cashing with a 10 bb stack or a 3/4 chance of cashing a 20+ bb stack. which do you think gives you the better opportunity to profit in the long run?
you might think 4 chances are better than 3, but does a 10 bb stack play the same as a 20 bb stack? what can a 20 bb stack do, as far as chip accumulation, better than a 10 bb stack? which stack sizes benefits more from a double up? what if you're card dead, which stack handle having to fold a lot of
hands? these are all things you to think about. it's not impossible to run well with 10 bbs, but you have a much better chance to run well with 20 bbs at the cost of not cashing 1/4 times.
it's not just what you can profit now, it's the potential profit you're allowing yourself to gain. but you don't get you see that potential if you're folding qq on the bubble as a short stack. majority of the time, on the bubble as a short stack, you're going to get dealt bad hands and you're going to fold into the money. you don't need to fold hands as strong as qq, in this spot, because it doesn't happen a lot. maximize your opportunity and potential to run deep, make ft, and earn a much bigger profit.
