I work on embedded software and far more often there's no good reason. (the global variables thing is ambiguous: it could be just counting static variables with well-defined scopes and encapsulation, or it could be describing truely global variables which can be modified by any part of the code at any time. The former is a reasonable technique to seperate modules without allocation. The latter is hair-raisingly reckless software design and also probably the more common approach, even in safety-critical systems). The level of awareness of software engineering concepts in the embedded ecosystem seems far lower than other areas.