The blue ray disc have had only a fraction of market penetration in UK that they have had in UK. Yes the picture is better but its not comparable to the differance between low resolution VHS and DVD.
Of course the makers would like us to regard our DVDs as obsoleat and replace them all -given them yet a third chance after VHS and DVD to resale their library back catalouge. To encourage this they have cut back on the special bonus features-eg deleted scenes, making of , langauge options ,related documentries and now you can often only get them on the blue ray versions. This is nothing to do with storage capacity. Its like two disc versions of DVDs most could have been held on a single dual layer disc, but two discs version make it seem more so they can charge more.
The only ones i will by are the Disney masterpieces like Snow White with the special features and the 3D blue ray editions such as Final Destination 4 which do benafit from high definition.