Why the concept of missing index groups is provided in SQL Server? I know about missing indexes, and that each index belongs to a missing index group which has a unique handle identifier. I want to know why groups are useful when we can just deal with individual missing indexes and what category or attribute of an index puts multiple missing indexes in the same group(cause there is usually one index in a group). Why it is comfortable to keep several missing indexes in the same group?

Thanks for your time!
This was a planned feature that never was implemented (the group concept), but the meta-data (DMV structure) is still there.