Porque con el USB OTG se podrán hacer virguerías como poner un USB TDT con el chip RTL2832U y convertirlo en radio multibanda, se podrá escuchar AM, radioaficionados, pilotos, policía, etc...:
http://sdr.martinmarinov.info
Turn your mobile phone or tablet into an affordable and portable software defined radio scanner. Listen to live on air FM radio stations, weather reports, police, fire department and emergency stations, taxi traffic, airplane communications, audio of analogue TV broadcasts, HAM radio amateurs, digital broadcasts and many more! Depending on the hardware used, its radio frequency coverage could span between 50 MHz and 2.2 GHz. It currently demodulates WFM, AM, NFM, USB, LSB, DSB, CWU and CLW signals.
You need
USB digital TV (DVB-T) dongle with the RTL2832U chip. You may already have one of them laying around. They cost less than $10 (eBay search)
USB OTG (On-The-Go) cable - if you've ever connected a USB thumb drive to your Android device, you already have it. They are extremely cheap (eBay search)
Then you just need to connect the USB dongle to an antenna, and via the OTG cable to you Android device and run SDR Touch! It is that simple! Now you can listen to live radio on devices (like the Nexus 7) that don't have a built-in FM support!