Why missile arsenals can undermine amphibious ships

Is a heavily missile-armed amphibious support ship a good way to add firepower?

It is an interesting option, but loading more missiles onto an amphibious ship makes a vessel that must approach the coast a more attractive target.

The proposed Marine Corps concept puts several missile systems aboard a new amphibious vessel. Every added weapon raises the ship's value to an opponent. Amphibious warfare already requires ships to enter threatened coastal waters and remain close enough to support a landing. Turning the transport into a conspicuous arsenal can therefore work against the need to approach before the enemy treats it as a priority target.