When I put together my gravel bike I went with 1X12 gearing before 1X12 was common on gravel bikes. All my bikes are 1X12 now.

What prompted my question was getting on my new MTB for the first time and thinking the chain must have fallen off. I was spinning like mad and not getting anywhere, I almost fell over, and it wasn't even in the lowest gear. There is a minimum speed that I can still maintain control and, at some point, the gearing gets so low that I can't pedal fast enough to maintain that minimum speed.