Because of the effect and outcome of gambling as a risky activities where there can not be certainty of getting anything at the end of the day.
No one can have a definite advantage or outcome from gambling, if a gambler wins, he doesn't really benefit because if you count from defeat, all the wins are not comparable.
All gambling activities, whether it's games or betting, have a high risk, unless you only use a demo account, maybe risks can be avoided, but I'm not sure anyone can survive just playing with a demo account.
Gambling is a choice so we must be able to be responsible and accept the risk of what is our choice.
That is it and that the reason why gambling cant and shouldn't be taken as a steady source of income and for that it risk can be taken as a turning point and an obstacle that stands against gambling becoming a steady source of income.
Let's look away from gambling for income and just take it as a way of having fun and nothing other than that because there is no guarantee of winning at all times.