1 To modernize the Logo
Facebook's Creative Director Josh Higgins said that the company wanted to move towards a more modern logo.
2 To make the logo more friendly
Facebook believes the new logo looks more friendly and approachable to people.
3 Better suited for viewing on mobile
Howard Belk, co-chief executive and chief creative officer of branding firm Siegel+Gale said that the new logo is more suitable for display on mobile devices and that the change was mobile driven.
4 To reflect Facebook's future direction
Josh Higgins , Facebook's creative director, said 'We worked with Eric Olson — whose typeface Klavika was used in the original logo — and developed a custom typeface to reflect where we are now and where we are headed,'
5 To match its branding strategy
According to proper branding practices a company's logo should reflect it's core values. Facebook's team believed that the old logo doesn't effectively send the branding message they wanted to send and that's why they decided to change it. (See Why Google changed its logo in September 2015?)
6 Facebook wanted to be taken seriously in the early years
According to josh Higgins During its early years Facebook was just a startup that wanted to be taken seriously and this is why they used a logo that looked more serious. After they got established Facebook was able to afford using a friendly and playful logo to communicate its values.
7 Facebook's team believed an update is more than enough
Facebook's team explored many directions but ended up believing that this slight update is more than enough to support their branding strategy.
8 To make the logo clearer
Some people believe that Facebook also wanted to make its Logo clearer by leaving more white space and making the letters clearer. (See What Does Dominos Logo Mean?)