I think the main issue is, that you are not allowing yourself to win the maximum amount of money by buying in for less than 100BB.
Imagine a situation, where you bought in for 50BB. You are on the button holding AA, you raise to 3BB, sb folds and bb is a bit donkier player, who shoves for 100BB. Now you call only to find yourself against 27o. No suckout occurs and you double up to 100BB. Great right?
Imagine the same scenario, but you bought in for 100BB. Double up=200BB
Imagine the same scenario, but you both are 150BB deep. Double up=300BB
This is of course a really stupid example, but it applies also for example set mining, calling with suited connectors etc- they are not as profitable if your stack is low, because the rare times you hit your hand and would get paid, you again limit your maximum win to 50BB, which is not great.
Of course you could say "but that way I also can't lose more money". True, but isn't the point to be a winning player and not to think about inevitable losing moments? If you are afraid to buy in for 100BB at 20NL, then just play 10NL. Besides, I rarely see anybody buying in for just one 50BB bullet. Almost always they reload another 50BB which makes me wonder why not 100BB from the start.
Also, last but not least, you'll find yourself in pretty awkward spots postflop if you are f.e playing big pots multiway and on the flop there is already 2/3 of your stack in the middle.
Cheers!