Is a Consonant Voiced in Between Two Vowels?

The rules came up at a time when people were using typewriters. The idea was that if your kind of framework or if your rules used a smaller number of keystrokes, it was more preferable. So this is why you'll see rules like "a consonant goes to plus voice in between two vowels" But there's nothing in the rule that tells you, for example, why this should be motivated.