I rather have that on my HDD than a usb.
Same for me, I rather install Android on a hard drive because it is faster, more stable, and less likely to break compared to a USB flash drive which break if you bent the metal plug on it.
Having Android on a bootable USB can be useful if you own more than one computer which can boot from USB, or you want to on run Android on your school/work PC without installing programs or operating system on your work or school PC. A lot of schools and workplaces lockdown Windows where only the Tech staff can install stuff. Sometimes users can boot into an alternative operating system like Android or Ubuntu Linux from a CD or USB drive during startup.
Not really. To be honest, I haven't seen much of a reason to play any mobile games, let alone emulate them on PC.
Some mobile games have good storylines, and fun gameplay, so gamers who enjoy a mobile game on a phone or tablet will be more likely to want to play a mobile game on a PC with a bigger screen and with a more accurate mouse and keyboard after enjoying the game on their smartphone and tablet.
There are exclusive mobile games like KINGDOM HEARTS Unchained χ for Android, and iOS which has a different art style, gameplay, and storyline than the PS2 and Gameboy Advance versions of Kingdom Hearts. Fans of the Kingdom Hearts series who don't own a good Android or iOS smartphone or tablet, or prefer a bigger screen will most likely emulate KINGDOM HEARTS Unchained χ on Windows or Mac.
KH Unchained X Gamers need at least 1GB of free space to play KINGDOM HEARTS Unchained χ. A lot of users don't have 1GB of freespace on their phones because their storage is almost full. KINGDOM HEARTS Unchained χ also need a phone/tablet with Android 4.0.3 or a newer iOS device with a faster CPU, more RAM, and better video chip. Users of older Android, and iOS phones and tablets won't be able to play KH Unchained X.
Emulating or running Android on PC is the only way for gamers to play KH Unchained without buying a newer and Android or iOS device with more storage, a faster CPU, faster video chip, more RAM, and newer OS which can be expensive, and not worth it if you just plan on playing a few mobile games like KH Unchained, Final Fantasy Record Keeper, and Clash of Clans.