Turning programming into mindless drudgery where you just go down a checklist of best practices is the reason so many programs are crap. The apps by passionate solo developers who really pour themselves into their work tend to be better than the just-barely-passes-tests work you'll get out of a cog-in-the-machine enterprise coder who just wants to go home.
Otherwise, the projects that WhyDay is encouraging are meant to be creative. Without creativity, we stagnate. No one is suggesting that a 4kb implementation of X become part of standard libraries. However, there could be endlessly useful things learned from such exercises even if its just a creative outlet for many programmers.