Why is that, you ask? According to the folks at Xperia Blog, it turns out that this is because if you were to go with the 8GB model, after the operating system and the apps and features Sony installed on the phone, you’d basically only have 1.26GB of available space to work with, so unless you’re not planning on download apps, videos, or take any photos, this is definitely not enough.
As pointed out by Xperia Blog, this isn’t really as simple as deleting unwanted apps, no thanks to the fact that many of the apps are baked into the phone meaning that they can’t be removed. We suppose you could flash a new ROM onto the phone which should remove those apps but then again we’re not sure how much you’d have left.
We’re not sure what Sony can do about it, but a couple of years ago Samsung had the same issue with the Galaxy S4 and a software update helped free up some memory, and also gave users the option of moving apps onto a microSD. In any case like we said if you had your eye on the Xperia M4 Aqua, perhaps getting the 16GB is a better idea.