Why Is Early Exercise Generally Not Optimal for a Non-Dividend-Paying American Call Option?

For a non-dividend-paying asset, an American call option should generally not be exercised early because exercising sacrifices the remaining time value (extrinsic value) of the option. The option holder is better off selling the option itself, which includes both intrinsic and extrinsic value, rather than exercising and only receiving the intrinsic value.

This principle is due to the option's leverage and time value.