Why were Hood's submerged torpedo tubes removed?

Did removing Hood's submerged torpedo tubes signal a change in her assignments?

No; it primarily meant that the weight could be put to better use elsewhere.

The viewer asks whether removing Hood's submerged torpedo tubes while fitting above-water weapons signalled a changing mission. The answer is no: the navy had better uses for the weight tied up in the submerged installation. This separates a refit tradeoff from a wholesale reclassification of the ship. Removing one weapon does not establish a new doctrine without considering weight, access, and competing equipment.