Yup, avoiding gambling sites would mean safe for your money, nothing beats that... But others don't do that since they are into gambling and might be obsess in winning big so they forgot about that way... Exploits are really safe, however there is no way that it would last long, gambling operators will always figure it out and patch, there is also a possibility that they might ban you from betting if they found out that you find an exploit and yet you keep on cheating...
Gambling, just like in life as a whole, the winner is the one with most experiences and is wise enough to do the things that works and not keep on doing things that isn't working. When you gamble and find a good strategy that you have the good odds against the casino, use it until it no longer works - which will eventually does because of the casino house edge.
Even you use a safe method it will not guarantee you 100% win. Having experience and being wise is effective in betting in sports but again it will not guarantee 100% win even you bet in a team with 99% winning chance there is still a chance that you will lose.