How Can Something Safe Also Be Incredibly Risky

If something is safe, but has a low probability of risk, then do it often enough and the risk factor rises.

For example, if you smoke one time, it's not a big deal. But if you do it one time and like it, then you are likely to do it over and over again, in which case the risk of various diseases goes up significantly.

Likewise, if you cross the street unlawfully or without regard for approaching traffic one time, you are probably safe. If you do your whole life, you are still relatively safe. But the whole world were to jaywalk all the time, we would be in a grave danger.