Functions are the meat of your application and classes are more like the plate. It's messy to eat meat without a plate. But if you don't have any meat, you don't have a meal.
If you have 500 functions in your applications, you're probably going to want to group at least half of them into larger collections for ease of access. You can devise common naming conventions ("Encryption_Encrypt", "Encycryption_Decrypt", etc.)...but classes are just easier. If you only have 12 functions in your application, you could probably survive with only 1 or classes, if any.
I don't often need to store data/properties in classes. I tend to store those in the database. So I haven't take advantage of that aspect of classes very often.
Classes also allow polymorphism, which can be helpful. If you have several classes that are extremely similar, or several variations on a class, you can save code...without having to construct some multi-purpose, Frankenstein-like class.