Why Is Exercising an American Call Option Early to Capture a Large In-the-Money Value Still Usually a Poor Decision?

Exercising early to capture intrinsic value is poor because the option's premium already includes the intrinsic value plus the remaining time value. By exercising, the holder only receives the intrinsic value and forfeits the time value.

The financially superior action is almost always to sell the option, which allows the holder to capture both the intrinsic and time value components of the premium.