In his letter to Amazon shareholders following the 2015 fiscal year, Jeff Bezos made a brief statement that all leaders should take note of: "We want Prime to be such a good value, you'd be irresponsible not to be a member."

It can be tempting to gloss over the sentence as puffery. Don't. The philosophy behind those words is a major driver to Amazon's rapid growth with revenues exceeding $100 billion a year.

The more value your business adds, the more customers you will win. And not just new customers. This approach will help you earn the loyalty of your existing customers over and over again.

Loyal customers are exactly what you want. They buy more, tell others about you, and they cost less to service and maintain. It's a win all around.

Here are three great reasons why great leaders focus relentlessly on delivering value:

1. It puts your focus squarely on your customer.

It can be easy to get caught up stressing about profitability, managing costs, or even how to get the right kind of publicity for your products. While all these areas have their place in managing your business, they should all take a backseat to one thing: serving your customer.

Business is about adding value. And if you don't have an offering that is valuable enough to get and keep the people your business serves, then none of those other metrics matter.

That's also at the core of Amazon's philosophy. Here's Bezos explaining why it's so essential to what they do:

"There are many ways to center a business. You can be competitor focused, you can be product focused, you can be technology focused, you can be business model focused, and there are more. But in my view, obsessive customer focus is by far the most protective of Day 1 vitality.

"Why? There are many advantages to a customer-centric approach, but here's the big one: customers are always beautifully, wonderfully dissatisfied, even when they report being happy and business is great."

The more your customers experience discontent, the more opportunities you have to make life better for them.

2. It compels you to innovate.

Peter Drucker is commonly known as the father of modern day business management. In one of his classic writings, he noted, "Because the purpose of business is to create a customer, the business enterprise has two -- and only two -- basic functions: marketing and innovation."

You can't afford not to innovate. But you're not innovating for innovation's sake. You're doing it to improve upon what already exists or to fulfill a gaping void in the market.

The more you innovate, the more you position yourself to solve your customers' problems like none other. The more you innovate, the more value you add. The more you innovate, the more relevant you are.

Here's Bezos again on why innovation is paramount at Amazon:

"Even when they don't yet know it, customers want something better, and your desire to delight customers will drive you to invent on their behalf. No customer ever asked Amazon to create the Prime membership program, but it sure turns out they wanted it, and I could give you many such examples."

3. It makes you indispensable.

A big part of earning customer loyalty is figuring out a way to seamlessly integrate yourself into their world.

The more your customers see your products and services as something they can't even bear the thought of living without, the less they will be willing to part ways with you.

That means constantly being on the lookout for ways to delight them, and make choosing you a no-brainer.

Here's what that looks like in action for a few Amazon Prime members:

Focus on deliver an insane amount of value to your customers. Over and over again. You won't go wrong when you do.

That's how you build a business that keeps your customers coming back to you again and again.