The engine dislikes the King Gambit, which has a pretty lengthy history, dating back to the 1600s [1]. However, it's not played much anymore at very top levels, and much has been written about its weaknesses [2]. So in some sense, humans have been "trying" the King's Gambit for centuries and have only recently come to the conclusion that it's not optimal.

Many players enjoy using the opening simply because it leads to dangerous and exciting games, so it makes sense that Stockfish and other engines would prefer conservative opening lines.

[1] https://en.wikipedia.org/wiki/King's_Gambit

[2] http://chess.stackexchange.com/questions/94/why-is-the-kings...