(sorry, I didn't notice this reply back there)
there's a reason attachments are so widely used - it's EASY
1) It's also easy to just drive your car, never changing the oil, checking the brakes, etc. That doesn't mean it's the proper way to handle the tool (your car).
Easy is not necessarily correct.
2) It's also easy to prop doors open when you're moving into/out of a building. They heavily discourage this at dorms in urban college campuses. Sure, it's easy. And every year, someone does it. And every year, some local criminal uses it as an easy way to sneak into the building. If everyone's lucky, it only results in some theft. It occasionally results in a rape.
Easy is often "not safe". (easy is, in fact, often the opposite of safe/secure).
Both of those lessons apply to email attachments. Email is not a "file transfer protocol", nor a "file sharing protocol". It also offers little to no protection of the message in-transit (there are ways around that, but none of them are perfect, and none of them offer long term protection), meaning it's also not a safe mechanism for file sharing/protection. It also offers no optimizations nor integrations with file management mechanisms, making it a resource pig when it comes to trying to shoe-horn "file storage/sharing/transfer" into email protocols.
Really. People who think that email is "a great way to share files" are on the same intellectual level as people who drive their cars, without maintenance, until the engine literally falls apart ... and/or people whose selfish short-sighted pursuit of their own convenience gets other people robbed.
(no, I don't consider that last bit to be sensationalist nor an exaggeration, considering the number of people I've seen wanting to send passwords, financial information, or health information, through email systems).