Orcs do go to Mandos, but no one except the Doomsman is happy to see them there:
the elves of Beleriand loathe them as ancient enemies, excepting for those who fear them as ancient enemies;
the rare Aman elves in the Halls have less personal experience with orcs and are usually correspondingly less overtly hostile, but still tend to assume orcs are stupid, ugly brutes with no redeeming features and so condescend accordingly;
and orcs themselves are seldom happy to see each other, due to a long history of leadership deliberately fostering a culture of backstabbing, selfishness, sadism, occasional cannibalism, and an extreme take on Might Makes Right, since the strongest person was always Morgoth or his eventual heir Sauron.
For most orcs, the Halls of Mandos are the first taste they’ve ever had of peace and they have no idea what to make of it.
Orcs In the Halls
the elves of Beleriand loathe them as ancient enemies, excepting for those who fear them as ancient enemies;
the rare Aman elves in the Halls have less personal experience with orcs and are usually correspondingly less overtly hostile, but still tend to assume orcs are stupid, ugly brutes with no redeeming features and so condescend accordingly;
and orcs themselves are seldom happy to see each other, due to a long history of leadership deliberately fostering a culture of backstabbing, selfishness, sadism, occasional cannibalism, and an extreme take on Might Makes Right, since the strongest person was always Morgoth or his eventual heir Sauron.
For most orcs, the Halls of Mandos are the first taste they’ve ever had of peace and they have no idea what to make of it.
No matter; Namo has eternity to teach them.