The Mishnah also explains that ships are not subject to being ritually unclean. The gemara contrasts it to a sack which can be carried both full and empty – but a ship cannot be carried, it carries! Fine but what about a canoe which can be carried both full and empty? Ah… there is a digression:
Rab Judah said in Rab's name: One should never abstain from [attendance at] the Beth Hamidrash even for a single hour, for lo! how many years was this Mishnah learnt in the Beth Hamidrash without its reason being revealed, until R. Hanina b. Akiba came and elucidated it.
The answer is less important than the lesson: one never knows when an opportunity for learning, for enlightenment, may arise. This is learned from the text:
This is the Torah, when a man dies in a tent . . .(Num. 19:14).
[That is to say,] even in the hour of death one should be engaged in [the study of] the Torah.
This was a rabbinic ideal – there is always an opportunity to learn. And learning is valuable for its own sake.