Yes, I agree with this, that everyone will always have different levels of tolerance for the risks they can take. It is based on many factors, one of which is the amount of income they earn each month.
However, the lower the risk we can take, in my opinion, the better, I mean for example we can take a risk of 5% of the amount of income, but we only take 2 to 3%. Now this is a wiser decision, because the rest can be our reserve fund.
Unfortunately, most gamblers do not consider their income when determining their level of risk, instead opting to follow others. Some people simply want to gamble without worrying about the percentage of risk they assume. As you mentioned, one gambler may stake $100, which may be only 5% of his income, whereas another gambler may gamble $100, which could be 100% of his income. This is why some people go above and beyond in displaying obnoxious behavior when they lose because they have lost all of their money through gambling.
Gamblers must conduct a self-assessment, which includes knowing their income level, responsibilities, number of dependents, level of emotion, and so on. If all of this is taken into account, it will go a long way toward determining the level of risk he can tolerate and staying disciplined enough not to exceed that level.