I work at a consulting firm.
Our salary is loosely linked to what percentage of our work is billable (with leniency for inexperienced staff, who aren't expected to be profitable while they're learning their craft).
If you spend three hours figuring out why things fall apart on the 31st of the month... that generally can't be billed to the client, and therefore it's bad for your salary.
On the other hand, if you spend three hundred hours writing tests and implementing an awesome multi-stage deployment process that avoids one production bug a month? Your manager can totally bill that work (with the right client).