So many revivals - what is going on?

There seems to be a trend - quite recently - to revive long, long ago perfumes. Case in point, the Oriza L. Legrand line. Some are supposed to be "the original formula", well, I suppose slightly tweaked and modernized, but true. This morning I noticed in Kafka's blog a revival - albeit not really successful - of "Tabac Blond" by Caron.

http://akafkaesquelife.wordpress.com/2014/01/07/caron-tabac-blond-parfum-modern-extrait-version/

I am not at all unhappy with the modern version of "La Route d'Emeraude" by Isabey, also close to the original formula.

These are examples of perfumes from the early part of the last century. Some firms have seen the light that these may sell well, because of the fact that the originals surely cannot be obtained anymore.

When will come the time that perfumes are issued, say from the Eighties, also with the claim "close or almost identical to the original formula"? If it is possible to recreate some from 1920, then why not from 1980? The same CIVET, OAKMOSS or other objectionable ingredients are in both alike? So, tweak it, if you must, but give me my "Opium", "Cinnabar", "Maja", "Calandre" ... too many to mention, those that I cry about that they are only a shadow of their original formula.