Using classes vs. using functions
It's a design choice.
A class is "meant to be" a collection that encapsulates functionality and "behavior" in code. The purpose is to expose specifically an interface where a class's instances can live on their own.  

A function/method is an independent piece of code that in theory "shouldn't" relate to other pieces of code outside of it.  

So for the example you've described, you could create a class named "User". And user can include these functions as it's members.
This does make it more readable and easier to debug.
However do not take unrelated functions and dump them into a class just cuz!
Examples are utility type functions, they could be kept in the vicinity of each other but should not be clubbed together as a class.

An additional benefit of classes is that they can be Inherited from. So more complex classes can inherit the basic functionality and add to it, while using the features already in the base class. You can achieve a similar effect by having "higher" versions of functions that calls more basic level functions. There again at least in my design perspective, I make a class where the whole functionality will be inherited as opposed to functions that are stand-alone.