IIRC there was something about how the scammers don't bother making their scams that legitimate looking, because if they are too legit, they get a lot of people who waste the scammer's time during the next phases.

But yeah, you'd think spam filtering would be more important. I use GMail and I haven't seen a spam message in years, besides when I check my spam folder. Even there, most of the "spam" is false positives.