I don't change the amount I bet when I play slots because I still enjoy it. Those who gradually increase their amount of bet might be those who can afford it, but I can't. But I could say that even if I bet the same amount at each roll, I have won many high multipliers in 5 digits and it was so damn satisfying when I received it. It's because I didn't need to force my way into doing a "martingale-like" bet. What I bet is enough for me, and I don't want to risk too much that I cannot afford anymore.
I think it all depends on each gambler's purpose. If he is really there to win as quickly as he wants to, then he might do the same trick as you said.
Maintaining the same amount as your stake is the best way to gamble especially when you are playing slots. There are people that can are capable of increasing their stakes as they progress but this can be detrimental even if you are doing it for fun. There are no tricks to win in casino gambling, this is something a lot of gamblers fail to understand. You can only get lucky and this cannot be chased.
The best way to gamble is to understand what gambling is, so there will be no excessive behavior in gambling, many people who pursue victory are people who view gambling wrongly where they usually view gambling as a means to make a profit even though it is not like that.
We can get a win when we are just lucky, especially with the type of slot gambling that really depends on luck, besides that I agree with what you said there is no special and surefire trick to be able to win at gambling, but only luck can make us win, the rest we must be able to set limits so that everything is under good control.