In the Italian game, according to the Lichess masters database, the play usually starts similarly to
[FEN ""] 1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 Nf6 5. d3 d6 6. O-O O-O 7. Bb3
However, this completely ignores the threat of Bg4, that can be played by black after 5... d6. This pin is somewhat nasty, since it can't be broken by retreating the light-squared bishop to e2 and breaking the pin by h3 followed by g4 weakens the kingside considerably.
I also remember some chess video recommending beginners to play h3 as soon as black plays d6 in the Italian game. Interestingly, Stockfish evaluates this position after playing 7... Bg4 as roughly +0.5, so 7... Bg4 is an inaccuracy. Actually, the engine also claims that after 7... a6 8. Bg5 an analogous pin from white also leads from white's slight advantage to an equality.
Why do masters (and higher-rated players) ignore the threat of Bg4?