There are a number of benefits of unlocking your phone. If you’re a frequent traveller, then an unlocked phone is a must as it allows you to use a pre-paid SIM card for a local carrier, which helps you avoid astronomical roaming fees. 

Some users also prefer unlocked phones because of the flexibility that they give you with your carrier: if you bought your unlocked phone for full price (i.e. you did not buy it with a subsidy from your carrier), you can sign a month-to-month agreement with your carrier, and switch at your leisure – whether that’s a bad customer service call, to take advantage of a competitor’s offer, or because you’re leaving the country.