Heres my thoughts on this.
Back in 1988 my mates and I got our first MTBs - a collection or Ridgebacks (601/2's - remember those), Specialized Rockhoppers and Saracen Trekkers. We all thought our bikes were indestructable - we rode them everywhere and we rode them hard. Some of us progressed and started racing :shock:
FF to 1990 every event we went to in what was to became NPS had XC, DH, Hillclimb, Trials and later Dual Slalom. Some of us entered all the disciplines but still all owned only one bike :shock:
I remember racing the 1991 NC at Beddgelert (Snowdonia) and pretty sure it was the first time DH was included. It was basically a fireroad but it was the first time I ever prepped my bike for a 'specialist' event - I fitted a 52 tooth chainring. As it was and due to the course a Raleigh road pro won it anyway :roll:
But that was it - the thin end of the growing wedge. People started prepping bikes for events. Soon we all had DH and XC bikes - mine were the same DBR Axis and Axis Pro but one had shocks. Some of my mates had specialist dual slalom rigs. And then bikes started to evolve and I'll get to my point.
Nowadays anyone starting to ride MTBS thinks that for their bike to be indestructable it has to have 5" of travel. They look at fully rigid or even short travel hardtails as not being up to the job. I laugh when I ride my regular loop on one of my retro bikes - all the other guys on Modern 5" travel bikes - the biggest drops offs there aren't even hardcore enough to damage my Discdrive
DH didn't kill the sport - the sport almost hit self destruct, ably assisted by the corporates who kept pushing us to buy more and creating a perception that "you need 5" of travel to ride offroad sir!"*
(*and maybe if you live in Fort William or Durango or Les Arc you do. On the Dunstable Downs I know you don't!)