Facebook's (NASDAQ:FB) taken a lot of heat recently for unbundling its messaging app from its main mobile app. The current version has an abysmal one and half-star rating, and many comments on Apple's App Store are anything but positive.

With all the backlash, the question remains as to why Facebook would separate out its messaging app. The short answer: Mobile users are fickle, and Facebook needs to stay nimble to keep up with changing preferences.

Facebook Messenger
Source: Facebook.

The changing face of Facebook
Facebook is no longer a social media website, it's a social media company. So while the Facebook site and app may be the flagship products, the company is extremely committed to branching out into new social media avenues.

Take, for example, Facebook's $3 billion bid for Snapchat last year. The company spotted something people were using and tried to jump on it. It didn't work out, but Facebook moved on and purchased the messaging app, WhatsApp, for a cool $19 billion. Before that it paid $1 billion for Instagram.

The company also created Facebook Paper, which incorporates some of Facebook's features along with curated content, and most recently launched Slingshot. Meanwhile, Instagram debuted its time-lapse video app, Hyperlapse.

The point of all of this is for Facebook to stay relevant by introducing (and buying) new products in an ever-changing social media landscape.

Don't shoot the Messenger
Recent data from iStrategyLabs shows that Facebook users aged 13-24 are leaving the social media platform, though other age groups have increased usage.

Facebook Users
Image source: Statista.

Kicking Messenger out of the Facebook app is just one way to help keep users engaged with Facebook even if they aren't keen on the platform itself.

The unbundling of Messenger is more than just a few age groups moving away from Facebook. There's an overall shift from traditional social media sites to messaging apps.

In an interview with CNBC a few months ago, IDC analyst Claus Mortensen said, "The likes of WhatsApp, WeChat, Kakao Talk and Line-are the future of social networking. They are the next breed of social networks, especially in emerging Asia where the use of social networks is highly mobile."

The article went on to say that messaging apps are expected to generate $25 billion in revenue by 2017 -- up from about $1 billion currently. Messaging apps generate revenue from variety of sources, with gaming coming out on top.

Line, a Japanese-based messaging app generated $340 million in revenue last year, mainly from gaming. But the company also sells stickers for users to send to each other and charges for promotional messages . A popular messaging app in China, WeChat, has an electronic payments feature that collects a small processing fee for each transaction. Right now, many messaging apps are testing out some, or all, of these options to determine how make revenue from their apps, but gaming seems the most promising. 

Facebook posted revenue of $2.91 billion and 1.32 billion monthly active users in the quarter ending in June, so generating small amounts of revenue from Messenger isn't likely a top priority right now. But making Messenger a stand-alone app -- as well as buying WhatsApp -- keeps Facebook on the cutting edge of the burgeoning messaging app trend.

The big picture
Despite Facebook's current success, the company knows it needs to stay nimble. Detaching Messenger is just one small part of that. As users shift their preferences toward other apps, you can expect the company to adapt with them.

Facebook released this graphic shortly after purchasing WhatsApp, showing the messaging app's growth four years after launch, compared to other popular products:

Facebook Whatsapp
Source: Facebook.

That's impressive growth over just a few years. WhatsApp has about 500 million users (compared to Facebook Messenger's 200 million monthly active users), adds one million new users everyday, and its messaging volume nearly matches those of global telecom text messages.

So while some users are angry about Facebook making Messenger it's own app, the company knows that it needed to do so to better compete with other messaging apps. By diversifying itself with Messenger and WhatsApp, the company is in a much better position to benefit from evolving messaging trends in ways that it could never do with Messenger glued to the Facebook platform.

What's still to be determined is how Facebook can make money from Messenger. Facebook CEO, Mark Zuckerberg, said on a conference call in July that "over time there will be some overlap between that and payments." When and how that will pan out is still unclear, but pushing Messenger out on its own would make a payment system much easier than if it were tied to the main Facebook app.

Chris Neiger has no position in any stocks mentioned. The Motley Fool recommends Apple, Facebook, Google (A shares), Google (C shares), and Twitter. The Motley Fool owns shares of Apple, Facebook, Google (A shares), Google (C shares), and Twitter. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.