8GB isn't much. By the time the 8GB is formatted and the OS is flashed, you'll have at most 4.7 GB. Android takes approximately 2.3 GB and the other 1 GB is formatting. All manufacturers do this. Storage isn't always easy to understand, but if you did you would see it makes sense. If you want more apps and music and photos, you need a microSD card. Then you can put music and photos and some apps.

The tl;dr part.

Memory is composed of bits and bytes, each byte containing 8 bits. There are 1,000 bytes in a kilobyte, 1,000 kilobytes in a megabyte, 1000 megabytes in a gigabyte, and so on. So, by the time you get to a gigabyte, what's 1000x1000x1000? 1,000,000,000. Each one of those bytes contains 8 bits, so it's actually 8,000,000,000 bits. Each bit represents either a 1 or a 0, which is fed through the system very, very fast. A processor has millions of on/off switches, and the 1 or 0 switches them on or off, resulting in what you see as processed data, after it has been processed to smithereens.

Part two: storage algorithms

You can't just dump your Minecraft save data onto your storage IC, simply because it would be understood by the processor. You'll need algorithms that store the data in a fashion that the processor can understand. This is called a filesystem. Depending on the filesystem you use, the speed of the memory may vary, as will the capacity. The capacity is reduced, because the filesystem needs space to store the algorithms it uses to store data. NTFS, FAT32, exFAT are a few of the popular filesystems for flash drives. Technically you can just dump your Minecraft save onto your memory, but in an orderly fashion, and very slow to retrieve.

Part three: the operating system (OS).

Every computer needs an interface, right? The processor needs something to manage the system and provide it with how and what to process. OS's are quite complex, so if you want to learn more just google operating system and chomp down. For Android, it will take about 2.3 or so gigabytes.

Last but not least, don't forget where you store your apps is storage, not memory. Storage is memory, but memory isn't storage.

Hope this helps!