It adds a level of stability. Some institutional investors don't want shareholders to have power over a company because that opens the doors to things like hostile takeovers. Having all the voting power vested in the core "founders" means the company won't ever be subject to change from outside. So, if you like things as they are, you can rest assured that things likely will never change. Only a long term investor, someone willing to retain shares during a corporate crisis, really cares about actually voting out one board for another. A short term investor wants to ride on the coattails but will jump rather than attempt to change where those coattails are headed.
That power is still there. By selling their non-voting shares investors lower their price, which has knock-on impacts on the corporation. What is lost is the power to directly make corporate decisions.
Definitely not for individual-saving-for-retirement investors IMO (altough there might be some that think that's important, but they can't affect nothing really).
What matters most to these (me included) is the growth of the nest egg, by dividends or capital gains (which FB has delivered handsomely on the last decade).
For large institutional investors, it may be important. For activist investors, it certainly is.
