Seriously though, while the worldwide spam volume seems to be trending down since a peak over 70% in 2014, rates were trending up in the first quarter of 2016 and the percentage of email that is spam or malicious is well over 50%.
Email, along with malicious files on websites (whose links are usually delivered through email!), continue to be the top malware vectors.
In fact, attackers don't even need to use their best, or most complex, attack methods. It's far more cost-effective to send out random or targeted email, or to place random malicious files on websites and email out the links. Remember, most cybercrime is economically motivated. It's a business and the goal is ROI (return on investment). And business is good.
It's a big problem because we are fundamentally trusting beings. I've always believed that people want to do the right thing. When it comes to people, we should assume positive intent.
However, email is not a person.