When you have the limits and you have control over your activities it is possible to make regular earning from gambling. From my experience as a gambler who tries to earn from gambling, it is really hard when your capital is small. When you've got atleast $1000 it is possible to make $10 regularly. Beyond that is kind of risk, so based on the capital will be our chance of regular earning.
It all depends on a gambler's attitude, if they can't control themselves and don't have limits then they can't get the profit or income but if they can make good use of gambling and have the skills to be able to create opportunities to win then gambling can be profitable even if it's not so big.
Sometimes a gamblers wants big profits, for example they have capital of $10, they want to double their money to $50 or more, so gamblers like this always lose control over themselves to get a steady income from gambling.
It's not necessarily that small capital is difficult to make a profits. In fact, with small capital we can try our luck without any fear of losing that money. In fact, sometime large capital is too risk if we lose control. It's better to use money with small capital to be able to get income.
I agree with what you said, They may be able to benefit from gambling if they have good limits and self-control in gambling, but if for a regular income I don't think so, because luck is also not always with them, I mean even if they have good self-control I don't think they will benefit if they are unlucky.
Trying your luck with small capital can be done as you said, I've experienced that, but it doesn't last long because the game is bad and also can't be cashed out because the balance I have doesn't reach the minimum withdrawal limit. They may be lucky if they try it with small capital, but keep in mind as you said that don't be afraid to lose money and luck won't come every time, Even if you use large capital, in my opinion, it makes us more courageous in the amount of bets, and will also make us unlikely to think about the amount of balance because it only focuses on the game that we bet a large amount. It's true that with bigger bets and bigger wins, but it's also how luck is, whether it's in favor or not at all.