I assume by CRM you mean customer relationship management? There main advantage is to keep all the information you need to deal with customers in one place, so that you don't miss out on opportunities by forgetting to get into contact with them.

These days it is important to be very organized. If you are a business with several employees you still want to be able to deal with customers when your account manager is away.

More subtle reasons for a CRM is that it allows the management to monitor the sales process, to analyze customer data for patterns, and to ensure that customer interaction quality remains consistent.

They can also be useful for ensuring that you comply with legal requirements as to accuracy of data if necessary.

Customer Relationship Management

CRM is the process of carefully managing detailed information about individual customers and all customer touch points to maximize customer loyalty.

Advantages:

- Identify prospects and customers
- Differentiate customers by needs and value to company
- Interact to improve knowledge
- Customize for each customer