There are times when non-technical people ( mostly ) or some over confident programmers for that matter, assume programming to be easy and that the program can be easily written. But the hidden complexity of the software is actually way beyond the estimated.
Ideating for application is very easy but giving it actual existence takes lots of pain. And that pain is discovered when actual work is started on the development side.
So when a complex program is assumed to be easy, its a event of Simple Matter of Programming.