Email is the single biggest vector for "hacks" and stealing money. Email is the biggest vector for spawning botnets. Heck, in half the email clients I see, there's no easy way to verify if <a href="phishingsite.com">your bank login</a> is a valid link to your actual bank or not.
Plus privacy issues, auto loading images (tracking pixels), accidentally reply-all, the ad-hoc way people think adding 50+ people to a CC list is a "mailing list," the way people think reply-all "+1 Adding Charlie" to the 50 people to add one new person to ad hoc email chain from hell is acceptable...
It's not good. It's just everywhere and people have accepted productivity killing social constructs around it so they can attempt to communicate at about a 60% effectiveness rate through such a broken medium.