1.Unlock your phone to be able to use any mobile network in the world. No matter which country or network you use – you can use it with your existing mobile phone
2.You can resell your unlocked mobile phone to anyone in any country unlike a locked phone that can be resold within the same country to people use the same network it came locked with.
3. Unlocked phones is a real bliss for international travellers/ business travellers since they need not pay high international roaming charges. Instead, they can use a local sim card of the travelling country.
4.Unlocking your phone is 100% legal and secure. No software to be installed, no hardware tampering!
Source : https://www.unlockninja.com/