Android 6.0 Marshmallow included a raft of new features, many of which were hidden below relatively limited cosmetic changes to the user interface. Amongst the improvements to the lock screen and the introduction of both the App Standby and Doze, designed to reduce power consumption and so extend battery life, Google implemented something called "Adoptable Storage." Adoptable Storage is the name given to the technology that allows the operating system to see an expandable memory card as internal storage rather than removable storage. This has a very big benefit in that applications cannot install themselves to an external memory card, even though the operating system will allow some data to be migrated across. In practical terms, Adoptable Storage can greatly increase the number of applications that may be installed onto a device with relatively limited internal storage, which in 2016 typically includes devices with a quoted 16GB of storage (as this is often reduced to under 12 GB after the operating system has been installed). Google added Adoptable Storage to greatly increase the utility of the Android One devices, which carry very limited internal storage: but adding a 32GB MicroSD card massively increases the number of applications that may be added.
Of course, there are complications associated with converting a MicroSD card to adoptable storage. There are three main issues and the first is that of performance, because the majority of MicroSD cards are nowhere near as quick as a lower or mid-range smartphone's internal storage, let alone a flagship device. This could slow down the device, introducing "jank" (the user interface dropping frames), lag or stuttering. Memory cards are also much slower to write to, so installing applications or performing upgrades might take significantly longer. The second issue is that of the user removing the MicroSD card from the device, which may well cause all third party applications to stop working or crash, and could cause the device to reboot. A third reason is that consumers could be confused by making a removable memory card essentially a permanent feature of the device, and should the memory card be removed, it is encrypted so as not to work in another device.
From Google's perspective, the company appears to consider expandable storage a necessary evil. It's cheaper to include a MicroSD card slot into an Android device than including a minimum of 32GB of internal storage, and customers love inexpensive devices - especially as Android is given away free. Some customers are perfectly happy with the stock applications and will not install third party applications, or even update the ones present on the device. Furthermore, Google operate a successful cloud storage platform, which is ultimately a business too. Android very much prefers being connected to a capacious cloud storage service and local storage is essentially used to cache data to and from this. We've seen manufacturers deciding to use or remove the Adoptable Storage system and as two examples, HTC included Adoptable Storage whereas Samsung have not.
Putting aside the batterygate issues Samsung have experienced with the Galaxy Note 7, this South Korean electronics conglomerate has been the most successful Android device manufacturer on the planet today. In addition to the flagship and headline-grabbing Galaxy S range, including the 2015 Samsung Galaxy S6 and the 2016 Samsung Galaxy S7, Samsung manufacture a huge range of lower and mid-range devices. And none of them include Adoptable Storage. With the Samsung Galaxy S7 family having a minimum internal storage of 32GB this is an inconvenience, but the manufacturer still sells devices with 8 GB of internal storage plus a MicroSD card slot. 8GB is at least halved to 4GB after the operating system, sometimes less and by the time the onboard applications have been updated, this often takes another gigabyte of storage, so customers are left with 2GB or perhaps 3GB for third party applications. Unfortunately, 3GB does not go very far when it comes to applications and soon, the device is reporting it cannot update applications as it has inadequate internal space. For models with 16GB, the situation is less dire but many, many customers will still struggle with limited internal storage.
Samsung are likely to face something of a shake up following the failure of the Galaxy Note 7: we may well see significant changes in how the business operates its smartphone business division. We have also seen the company explain to customers and investors time and time again about how they will put a focus onto their device software and although we have seen some improvements, when the Galaxy Note 7 wasn't catching on fire the user interface was not as smooth as we would expect from a flagship device. Perhaps 2016 can be the year that Samsung reintroduced a number of useful software features from stock Android that the company saw fit to remove, critically Adoptable Storage, and upgraded the minimum internal storage to 16GB for the low end handsets and to at least 32GB for mid-range devices.