I think you are being sarcastic, because I can balance a broom a lot better than a pencil on my finger, so I'm going to discuss my thoughts behind why.

Based on what you are saying and tomxor in a sibling comment. Stability seems to increase with scale. Maybe it has something to do with weight, or center of mass, or a combination of the two.

I know that the longer the object you are balancing upright on your finger (or palm for something bigger than a broom), the easier it is to compensate the shifts in center of mass as it tilts. For a pencil, technically i guess it is "easier" to balance if you are a machine able to make the fine micro adjustments required.