Where is this reluctance you speak of? Come on, know a bit of history before asking a silly question.
Just a short list of pieces that use the brass a heck of a lot and/or they are crucial to the effect.
Mahler 1, Mov. 4
Mahler 2, Mov. 5 (and 1 somewhat)
Mahler 3, Mov. 1
Mahler 5, Mov. 1, 2, 3, 5
Mahler 6, Mov. 1, 4
Mahler 7 (meh)
Mahler 8
Mahler 9, Mov. 3
Bruckner 7, Mov. 1, 2, 4
Bruckner 9, all of it.
Strauss' Don Juan
Strauss' Ein Heldenleben
Tchaikovsky 2, Mov. 4
Tchaikovsky 4, Mov. 1, 4
Tchaikovsky 6, Mov. 1, 3
Wagner, pretty much everything he ever wrote ever
Stravinsky: Rite
Stravinsky: Firebird
A bunch of other operas such as the Verdi you quoted.
Shostokovich 5, Mov. 4 (and 1 somewhat)
Berlioz: Requiem, Tuba Mirum
Berlioz: Symphonie Fantastique, Mov. 4 and 5
Respighi: Pines of Rome, part 4
Mussorgsky: Night on Bald Mountain
Mussorgsky: Pictures at an Exhibition, Catacombs, Great Gate of Kiev (and others)
Holst: Planets, Mars, Venus, Jupiter, Saturn, Uranus
I might as well name the entire Romantic period minus stupid composers like Grieg, Schumann, and Chopin who didn't use the brass sections effectively.
Any questions?