The real advantage of OOP, as used today in Java/C++, is instantiation. Instead of having procedures working on global variables, you have procedure working on local variables, including complex data structures.

Instantiation took some time to get widespread adoption. Originally, even local variables were actually global, scoped variables, thus forbidding even recursive calls (see earlier versions of FORTRAN). Programming languages since use a stack to instantiate their local variables (and return pointers), thus enabling recursion. The instantiation of more complex data structures (arrays, user defined structs…) followed.

Ironically, instantiation took some time to become ubiquitous in the C language even though it fully supported it from the very beginning, with a stack and user-defined compound types. Case in point: Lex/Yacc, which use global names (and state) by default.

Now however, instantiation is so pervasive (global variables are assumed evil by default), that we don't even call it OO any more. We just call it good practice.