Android 6.0 Marshmallow handles external storage, like microSD cards, in a new way called "Adoptable Storage." Samsung has issued a statement on why the Marshmallow-based Galaxy S7 and S7 Edge won't support this feature.
When Google first showed off Android 6.0 in May 2015, it was codenamed "Android M," and much of its focus was on under-the-hood improvements and polishing up the Material Design UI introduced in Android 5.0 Lollipop. Android 6.0 Marshmallow was the final name, and Google released the OS in October 2015 to coincide with the release of its latest Nexus smartphones, the Nexus 5X and Nexus 6P.
One of Android 6.0 Marshmallow's top features is "Doze," which automatically puts a device into a sleep state when it's not being used, greatly saving precious battery life. Another popular addition was "Now on Tap," which incorporates Google Now functionality throughout the OS, including third-party apps that support the feature.
Google also introduced a less-talked-about feature called "Adoptable Storage," which was designed to make Android 6.0 Marshmallow's way of handling external storage easier to understand for users. It works by merging the external memory (microSD) with internal memory, to serve as a single memory partition, which allows the OS to install apps and media as they are viewed as part of internal memory.
If you're used to the way Android handled external storage like microSD cards and plan on purchasing a Samsung Galaxy S7, S7 Edge or LG G5, which all run Android 6.0 Marshmallow, Samsung has issued a statement regarding why it chose not to institute "Adoptable Storage" in the Galaxy S7 and S7 Edge.
Android Authority noticed that the new LG G5 and Samsung Galaxy S7 and S7 Edge don't support Android 6.0 Marshmallow's "Adoptable Storage" feature and is reporting that Samsung did it for users' convenience when responding to questions about the issue.
"Samsung decided not to use the Android Marshmallow 'adoptable storage' model. We believe that our users want a microSD card to transfer files between their phone and other devices (laptop, tablet, etc.), especially the photos and videos they shoot with the camera.
With adoptable storage, first of all the card may be erased the first time it is inserted into the device. This behavior may be unexpected by many users and we don't want our users to lose their files. Second, once Marshmallow starts using a card for adoptable storage, it cannot be read by other devices, so it loses this ability to be used for file transfer. Adoptable Storage is also primarily targeted towards emerging markets where devices with only 4 (GB) to 8 GB of onboard storage are common. We think that our model of using microSD for mass storage is more in-line with our owner's (sic) desires and expectations for how microSD should behave."
While LG hasn't issued a statement on why the LG G5 won't support the feature, it's very likely it does not want to change something that's already working well and could potentially causes a headache for users who swap out microSD cards.