Umpire Takes Swift Softball To The Gonads And Goes Down Harder Than Monica Lewinsky In The Oval Office
When in doubt: wear a cup.
When NOT in doubt: wear a cup anyway, just in case.
When not umpiring for a softball game and therefore not in any danger of getting hit in the balls by a softball: wear a cup anyway, just in case, because you never know when your dick will be assaulted by an airborne object.
Tl;dr: If you value your dick, wear a cup.