I don't think the industry is dying....it's just leveling off
There are quite a few bikes you can buy new for under 8K. Some around $6000. Go try and find a new car for those prices. And many are still attracted to motorcycles for their gas mileage.
Looking at good used bikes, they are still pretty cheap (figuring in inflation) I bought my Bonneville (new) for about 7 grand. It's also quite popular with the hipster crowd it seems. I don't count figures on new bikes sold, look instead at bikes registered each year....the numbers aren't going down.
But yes, many people are tired of driving. Just owning a car (or bike) is a hassle to many now. They can see how poor of an investment one is. And I have to agree with them. If I lived in the city (and worked there) I'd likely own a small displacement scooter...if I just didn't want to ride a bicycle or take public transport.
But there are, and always will be, those attracted to two wheel machines.
"As of the most recent report by the Department of Transportation, there were 8,410,255 motorcycles registered in the United States by private citizens and commercial organizations in 2011. To put this staggering number into perspective, out of every 36 people you meet in the U.S., one of them probably has a motorcycle."
Also....name your favorite motorcycle ad on TV. "Well there's that Honda one where ...wait....that was a car ad.." I watch a lot of TV and I've never seen an ad from a motorcycle company since 1974. The only ads I've seen were on places like the Speed Channel...during the airing of a motorcycle race.
Saw no ads during the Super Bowl ... late night I think I saw an ad for a local Harely Dealer at 3am...but I could have been dreaming.
. Seems if you want to increase sales you'd need to advertise. Think how many bikes you might sell to women (an increasing market) If you had an ad showing Wonder Woman beat up some bad guys in an alley and then say to some woman on the street getting off a bike as she walked away "Nice bike"
I understand the Big Four might not have the sales volumes that car companies do to pay for television spots, but you'd think they'd squeeze one or two in a year and not just during motorcycle related programming.
And some interesting stats...although the amount of registered bikes has risen, the fatality rate has gone down:
https://crashstats.nhtsa.dot.gov/Api/Public/Publication/812292