It’s a good question. If you have read Sfeer & Loathing you will already know that The Warp Lords may cause a wave function collapse if they observe Schlock repairing the damage they have caused to Infinite Earths.
Consequently, the Quantum Mechanic prefers to operate in secret.
His work includes dismantling humans who are beyond repair, saving victims of the Warp and selecting and training humans to be Cosmic Enforcers.
Slayer also collects ancestral debts for the ‘sins of the fathers’. This is described on a personal, family and national level in the Epigenetics section of The Quantum Mechanic’s Galactic Handbook.
The Handbook strongly advises that Mechanics work behind the scenes wherever possible. This helps prevent ‘Messiah Syndrome’: where humans turn to the Mechanics for leadership.
Mechanics believe sentient species should take control of their own lives, be their own leaders, and decide their own destiny.
Slayer, like many Mechanics, will sometimes leave his symbol on a repair job. Or he may be seen, barely visible above the Quantum level, secretly observing humans.