If you are on rough, gravel roads, yes, the chain may fall off. A narrow/wide may help, but a clutch RD does most of the work with chain retention.

Or, you chain may not come off. If it does, stop the bike, put the chain back on. It ain't the end of the world and it ain't rocket science.

If you are on smooth road, there is zero worry about a chain magically coming off.