"Cloud" allows you to store your data off site and not on your device . this means you have more space on the device , you can access it from anywhere on the planet as long as you have Internet access. It also means your data , photos etc , are backed up and can be recovered. I've found many who hate the privacy issues and don't use cloud solutions don't use anything else ! and lose all there stuff when their device does ( they all will ) fail. The cloud allows set and forget back up
Most of the security issues are caused by people using simple passwords like celebrities using their dogs name .. Really? I'm sure nobody knows that!
Your welcome to most of my photos ( boring to outsiders ) music etc I don't keep credit info unencripted ( your in more danger handing your card to the waiter than storing on the web )
Do you need it ? No . should you use it ? Probably . it was designed for those who want a simple acces to their stuff ... No matter what.