In April 2013, NFL Execs took a look at over 70 prospective logos for the 2016 Super Bowl before eventually settling on the one above (that's true by the way). Since they found it hard to build an attractive logo around the Roman Numeral for 50 (which is "L") they opted to use actual numbers that people know without looking them up.
And lest you think Caesar is spinning in his grave (which, don't get us wrong, he is) that will eventually subside since the NFL is opting to go back to the stupid Roman Numeral system starting again in 2017. And that would be *looks it up* Super Bowl LI.
[via SF Gate]