A) It does not transmit or receive as effectively as a full-sized antenna
Many hams upgrade their HT's rubber duck with a higher performance antenna. The trade off is typically size for performance. However, there are times when a full size antenna is needed to make the contact. For example, Arrow have handheld 2m/440 Mhz Yagi's that work great with an HT and can be used for satellite communication.
|Directional arrow antenna for 2m/440 MHz|