Well I didn't say they needlessly has to make the diffrent maps boring for you It could basically be the same map just split up in 10 to give some sence of scope to the world and realism for that matter !!
If the map was split up it would run into the same problems lots of these sorts of games have. With smaller maps it’s very easy to tell when you’ve fully explored and exhausted an area. Because Larian’s maps are large and filled with little nooks and secrets, it’s easy to miss things, which makes it more rewarding to find them. Chopping up the map would diminish this.