Comment by marcosdumay

It's just not bothersome enough to deviate from the standard.

If they did this, nobody would use it. They do lots of more useful things that people don't use because it's not portable.

There's a sibling comment about temporal databases. Those solve a very bothersome problem, so a few people use them. That means that there's a chance soft deletes get adopted as a side effect of a much more complex standard.