As you said , bigger capital means bigger return to get and it avoids you for your money ran out in the house.
regardless whether you have the capital or not, gambling is always give you negative expect values. In another words, even if you have super big capital, you will still end up losing in the long run. And that is how the casino make money. If rich people can ensure that they win with big capital, the casino would have been bankrupt a lot of times.
Even then, if you have a big bankroll and proper control (which it seems a lot of people that gamble seem to be lacking), your expected value will be negative in the end simply because of the house edge.
Even in 50/50 odds to win, your actual odds are more likely to be somewhere near 49.5% to win (depending on the casino) because the casino needs to earn money for their service.
The only way you will ever win in gambling if you hit it big early in your gambling "carreer" and then never hit the tables again. But I guess most people don't have the guts to do this as it also feels too good to keep playing after such a win, thinking you can get even more.
That is right, it is very rare to find a person that will just gamble once like hit and run thing. Most of the people that will go gamble will play for a longer period of time before stopping. But of course, there are really people like that but as I have said, they are very rare kind of breed. This is a good thing but when they lost that first bet, I don't think so that they will go - for sure, they will chase their loses and that is the start of being hooked to gambling.