The value of a single rockets cargo can easily be worth more than a container ships cargo. The average TEU at Port of Los Angeles is worth ~43k USD and the words largest container ship is only 24k TEU, that’s up to 1 Billion in 2021 USD and plenty of satellites have been worth more than that.
The ships can be worth quite a bit when new, but their also depreciating assets with only a few percent of that in scrap value. Only using the least valuable ships in areas that can be pirates seems like an obvious optimization.