i occasionally need to compare two tabs. previously that meant that i had to open those two tabs in separate windows and then use window tiling to place them side by side. setting that up was a lot of work. and also it makes switching windows very hard. each side by side view would add two more windows that all need to be cycled through when i switch windows. and don't try to have more than two of those on a workspace. you'll go crazy switching between them.
with the split view it not only becomes very easy, but the split tabs also keep their position among all the other tabs, so i can keep the view permanently without cluttering up my list of windows. currently i have 5 split views in active use. that number is likely to grow...