If you happen to be an active trader or know people that trade actively, you will notice that traders do not easily give out money ( i.e lend out money) not because they don't have to give but because their capital is actively and most times always involved a trade.
You have to understand as a friend to traders that even in times when big wins are celebrated, it is not still a time to ask them to help you with money for your needs with the thought that they are in profit, because if you do you will get yourself disappointed nine times in ten chances.
Work for your own money, nobody owes you anything.
Not only this another reason why traders don't lend out money is because of the cost of capital, they always think of the return that they could earn on the money that they have lent to someone, this way they think that opportunity cost involved in giving someone that money isn't really justified which is why they decide not to lend out money anyone. Your point is quite valid too, generally, money is also engrossed in various trades, also when you take out money from your capital you also give your risk aversion and percentage a hit, which means you have to reduce your order value too.