Ships in which the pilot can leave the capsule do exist. Lore reference: Cross-capsule variant
I agree with Bjorn, though–a capsuleer walking around the ship would negate every benefit of the capsule. The pod is what allows the capsuleer to navigate the ship via mind. And the only way that the capsuleer’s mind can be transferred to a medical clone upon pod death is if the capsuleer is hooked up to the pod at the moment of pod breach. If s/he was walking around the ship when the ship was destroyed, s/he would die just like any other person.