Gambling is unpredictable. Thus, there is no single betting strategy that will lead to regular wins.
You can't generalize like that as there absolutely are people who make a living through sports betting. Maybe not OP (since they haven't shown proof), but legitimate professionals exist. These bettors consistently make quality picks and have proven long-term profitability. Just because most people lose doesn’t mean skilled, disciplined bettors can't win over time.
You are right, atleast I know a few guys who I believe to be professional gamblers here in my locality, but there are lapses which makes me believe that it's very risky to depend solely on sports betting as a means of income.
It maybe possible for a single person to depend solely on money he or she makes from betting, but it's absolutely not possible for married person with children to take care of to depend on something that's doesn't offer any form of guarantee when it come to making money, no matter how good or skilled they seem to be with betting.
People I know who appear to be professionals bettors often have other businesses by the side the depend on in times when nothing seems to be coming out from their betting activities.