It's fair to say I've been vehicle enthusiast since their first introduction - and living without vehicles is, to me, the biggest sacrifice I've made by choosing to stay on Toulan full time. However, with vehicles, Toulan would be way too small. This exploring you talk about is quite rich on Toulan, precisely because of the vehicle ban.
Toulan is just a single server area. Next Island, not even counting Ancient Greece, is 5 times the size. The content on Toulan is very dense and that, combined with the geography, makes it feel much larger. Zooming around in Valks and Quads would destroy that sense of space.
If you want to really explore Toulan, think of old-school, pre-vehicle EU - stock up on Mind Essence and go. It takes longer - but it's not that a big a place.
Cheers,
Miles