When using double bonds (or triple bonds for that matter) there can be problems when the geometry of them is not linear:
They tend to intersect with other bonds or don't even connect to the other bonds because the double bond is bended (by e.g. ~90 degrees).
You can verify that by creating a propane structure and adding a double bound to the C2 position and then dragging that C2 position around.
When using double bonds (or triple bonds for that matter) there can be problems when the geometry of them is not linear: They tend to intersect with other bonds or don't even connect to the other bonds because the double bond is bended (by e.g. ~90 degrees).
You can verify that by creating a propane structure and adding a double bound to the C2 position and then dragging that C2 position around.