Data structures are used in computing to make it easy to locate and retrieve information. Primitive data structures are simple ways for programming languages to represent basic values. These include data types like integer, char (character), Boolean, pointers, and the like. Non-primitive data structures provide ways of storing multiple values in a single variable. These include arrays, lists, stacks, trees, and so forth. Data structures can also be used to group and organize other data structures. In databases, a record can be thought of as a data structure that contains all the data structures related to a given key; in object oriented programming languages like Java, a class is a data structure that organizes attributes and functions in such a way that they can be easily replicated. In each case, the way the data is "structured" makes it easy to retrieve or manipulate.
Data structure is a particular way of storing and organizing information in a computer so that it can be retrieved and used most productively.
Different kinds of data structures are meant for different kinds of applications, and some are highly specialized to specific tasks.
Data structures are important for the following reasons:
1. Data structures are used in almost every program or software system.
2. Specific data structures are essential ingredients of many efficient algorithms, and make possible the management of huge amounts of data, such as large integrated collection of databases.
3. Some programming languages emphasize data structures, rather than algorithms, as the key organizing factor in software design.
I believe the question relates to data structures as used in computer systems. In this field data structure refers to the way data is stored, and organized in computer systems. In computer systems we do not have the option of using or not using data structure. Computers has to store and use data. Computers cannot do without data, and wherever data exists it must have some kind of data structure. Thus instead of asking "what is the need of data structure", it would be more meaningful to ask "what is the importance of data structures".
Use of appropriate data structure enables a computer system to perform its task more efficiently, by influencing the ability of computer to store and retrieve data from any location in its memory. Different kind of data structures are suited to different computer applications and tasks.