Whether you're using an IPhone 4 or 5c, it's crucial that you back up the device frequently, because you never know when you'll land in a situation where the data on your phone could be thrown in jeopardy. This happened to a Pennsylvania customer of ours recently when his wife accidentally dropped the phone in the bathtub. Despite it only being submerged for a few seconds, when they removed it from the water it had stopped working.
Unfortunately, the man and his wife kept a lot of important content – including prized family photos – on the phone, and we gather from their repair request that the data exists there and there alone. The problem with only storing your iPhone's information on the phone itself is that there are so many conceivable situations where you'd lose that data. Whether it's dropping the phone in a tub or leaving it in a hot car all day, people find themselves in situations every day where a phone ceases to function. But by backing up that data to the cloud, you can avoid something like that ever happening.
As for the Pennsylvania couple, we'll work in our shop to recover any data we can.