'Cause a whole bunch of people don't know how to do security.
You'd be surprised how many people come up with this then don't think any further.
This is the kind of solution I see from new grads with no crypto/security experience, but whom with a quick frown, think about it a little more and suggest why this is a bad idea. Many can do that even when they don't know how exactly to do it correctly.
This was just lazy/rushed or dare I say it, negligent.