One? Two? Three?

When it comes to a movie, how many copies does a person need?  One? Two?  Apparently, we all need three copies of a single movie.  One Blue Ray copy, one DVD copy and one Digital copy.   I went to buy a movie that just came out Blue Ray.  I could not, for the life of me, find it on Blue Ray by itself.  I could buy it on a single DVD, but I have a Blue Ray player, so why would I buy a DVD copy?  In the end, I reluctantly bought the triple package sure never to use the DVD or Digital Copy.  I suppose I could find friends to give the superfluous copies to; but until then, they will take up space in my movie case.  I just wonder if I will have to go through this every time I want to buy a new release.