For the last few expansions now, we've seen that the only real method of getting to expansion continents is through portals or hearthstones.
The last time we saw boats and zeppelins to a new continent was in Wrath of the Lich King which had boats for the Alliance to Borean Tundra and Howling Fjord from Stormwind and Menethil Harbor respectively, while the Horde had Zeppelins to Borean Tundra and Howling Fjord from Orgrimmar and Undercity respectively.
After Wrath, we saw cataclysm which had zones scattered around Azeroth with the main mode of travel being portals in each faction's capital city, or flying to ones which existed in the main continents (if you so desired).
Mists of Pandaria then had a portal in each faction's capital once more, without any other option of travel to reach it. Once 5.1 came around and each faction established a coastal base in Krasarang Wilds, it could have made sense for each faction to have a ship to these locations.
Warlords of Draenor functioned similarly to TBC as it existed through the Dark Portal, except using the Dark Portal itself was incredibly janky in comparison for some reason, and also made zero sense anyway since the portal was destroyed in the introductory segment of the expansion. From there on we used portals to access the area once more (which in fairness is probably the only way this could have been done given how it played out).
Legion has our main access point to the Broken Isles being Dalaran, via portals from the factions capitals once more, or a hearthstone. Sure, the main hub is the capital of the Kirin Tor, so portals make a lot of sense, but it could have been nice if we had at least some form of manual transport to reach the continent.
Finally we have the upcoming expansion Battle for Azeroth, and at a guess, we will probably end up using portals again to reach Zandalar and Kul'tiras.
Personally I feel like having boats and zeppelins to continents that exist on Azeroth adds a little extra to the immersion, making it feel like you're actually travelling a great distance to a location rather than simply hopping through a portal and suddenly you're on the other side of the world, which is getting kinda boring and feels kinda lazy at this point.
So as with the title of the thread, why don't we see boats and zeppelins anymore?