why dont you make it so the map is slightly bigger every update wich has stuff that needs to be found, like when you added flowers, some people would have already explored the entire map, so they would haft to create a new world to have those features.

if the world  got a bit bigger every time time you added something to the world then we wouldn't half to create a new world

With each version, I just start all over for scratch.  

We are trying to maintain save files between versions because we know first-hand how much effort goes into making things. But @RuBlue3748 does have a point: it pays to be cautious :)