Negative present endings translated as past tense

I've seen certain translations where I feels like there's a shift in the tenses.

Ex: なぜ早く言わない!？ translated to "Why didn't you say so sooner!?"

In fact, I've experienced a lot of cases where a character says the word in it's negative present form in Japanese. For example, imagine a scene where a sibling fails to wake up the other for some big event. In this case, the other sibling would say "Why didn't you wake me up"(past) instead of "Why don't you wake me up"(nonpast). However, what I see instead in Japanese is 起きてくれない instead of 起きてくれなかった.

Any explanation on the system here would be appreciated.