Programmers take honor of HW guys

It is a famous anecdote: When programer go to sleep, he put close to bed one full glass with water, if he will want to drink, and one empty glass, if he will not. However, these are VHDL coders who should care about all branches. It is reasonable to assign new value in all branches to a signal to prevent latches. However, what is the need to cover all switch cases?