Vanilla WoW: We got no portals mostly, everything was done by foot.
TBC WoW: Big giant portal towards the continent
Wotlk Wow: We had a ship going towards the continent (best thing they ever did.)
Cata WoW: They used a portal towards each zone you went to.
MoP Wow: a whole new island to explore, yet we take this by a portal not a boat.
WoD WoW: we taking a portal once again.
Wouldn't be surprised if legion had a portal too instead of a boat. (haven't been checking beta)
There are few things that break WoW's immersion. Portals are one of the big ones on the list.