How many times have I been annoyed and delayed by having to ungroup something just to make a simple edit? Too many to count.
I often group many things together to aid in layout setup and positioning. Say you have a set of fields and objects that together make up a ‘widget’ or function (e.g. a custom calendar picker, or custom labeling for a radio button set, a set of fields for an address, etc), and you want to keep them all together in a particular arrangement. But then you might have to make a change to a font, or a hide condition, or a small tweak to the position of one item within the group. Now you can do all those adjustments without having to break the group and then re-group the objects when you are done!