Because it was a business decision to make it PG13 from the get go. Which means they had to write the entire thing that way from it's conception, meaning it's NOT Terminator. The entire process was effected from the beginning. It's almost worse than making an R film, then editing it.
It's not as simple as it was missing some blood and some F words. It's not about that. It was just stripped before it was even made, just so that kids 17 and under could go.
Yea, they are a business, but don't ruin a great franchise like that. If you wanna make Transformers, go make Transformers. Don't call it Terminator.