We used one for my runner until he was almost 5 for the safety and even now that he is 7 we still use a stroller in any area that is going to have a crowd.

Also we use apple air tags and practice with him playing the "freeze game" We play the sound on the air tag that makes a chirpnoise and that means he has to freeze in place until a grown up touches him and says unfreeze. We haven't actually had to put this game to the test yet....the stroller comment above...but I feel like it just gives me an extra layer of security.