You only use small amount of funds to gamble because the availability of big funds is actually not there because I know for certain that if you are truly a gambler then using huge amounts of funds to gamble wouldn't be a hassle for you because the more you stake the lesser odds and risk involved in winning that particular bet.
That's not the case for everybody and probably not the case for this user, gambling with big funds put you at a risk of losing a one time big amount of money that might affect your confidence to continue gambling. But when you use small capital and it get lost you can get over it.
We have different strategies to use in gambling, some gamblers use small capital and it favors them while other use large capital and it also favors them. You don't have to use a strategy that doesn't favor you just because using large capital reduces the odds and risk involved.
One mistakes gamblers make is to listen to advise online without test trying the advise to see if it'll favor them but they blindly follow the advise and before they realize it doesn't favor them, it might be late already and they would had lost a significantly higher sum of money.