Well, that's the thing: in customer facing (even if it's an internal "customer") occupations there's usually no other choice but be driven by external timings, but if you're doing software development or any other kind of thinking/creation work, frequent interruptions just break your concentration, pull you out of Flow (the psychological state of maximum productivity), force you to mentally switch tracks (a form of overhead cost) and often make you lose track of what you're doing, not to mention being a source of unecessary stress.

Unfortunatelly, whilst some are good, plenty of Engineering environments and managers are pretty bad when it comes to recognizing the costs of frequent interruptions and supporting a maximum productivity environment, from the systemic corporate-wide problem which is "open space" work areas to managers who themselves are overstressed firefighters with poor time, impulse and prioritization control, the kind of reactive unstructured behaviour that ends up disrupting everybody else's work flow.