This was probably Santiago's normal routine. He did not have much, but the limited amount of personal possessions he did have, he meant to keep. The narrator remarks that no one would steal from the old man but he (Santiago) would know that dew is bad for the cloth (sail and lines) and that even to tempt a would-be thief with any of his gear was not worth the risk:
No one would steal from the old man but it was better to take the sail and the heavy lines home as the dew was bad for them and, though he was quite sure no local people would steal from him, the old man thought that a gaff and a harpoon were needless temptations to leave in the boat.
It is also likely, but just one interpretation, that the old man took pride in his few possessions (especially those having to do with his profession) and it is likely that he took pride in carrying the mast from the boat to his shack: a literal and figurative "shouldering of the burden" which he gladly continues to do as long as he can continue to be a fisherman.