Airline miles are dying, but Hotel points are alive and well. It comes down to the fact that:
1). a meaningful elite status is much more easily attained & retained with hotel (via credit card, etc) than with airlines
2). it's a lot easier to be loyal to a hotel chain than airlines, since the fares, routes and schedule dictate your choice of airline much of the time

Furthermore, as has been pointed out, airlines have little incentives to keep up the mileage plan benefits when seats are full and there's decreasing competition. With a couple more iterations of devaluation and other rule changes, the concept of airline miles program will truly become meaningless. Except the existence of global alliances is probably tied to necessity of mileage plan... or maybe not.

My main airline program used to be UA, but it's becoming harder to even say that. >85% of my travel is personal, meaning I will fly almost exclusively in Y and choose my flights based on fare and convenience. I fly probably 60-90k most years. My hotel program is Hilton, and I stay at Hilton probably 20-30x a year.

Take UA for example. Back in the pre-merger days, it was easier to get Premier Gold (easier to earn more EQM) and the basic Premier meant a lot more (E+, etc). Now Premier Gold is impossible to attain, and Premier Silver is not a lot whole lot better than an Explorer card holder. Even if I hypothetically had a meaningful elite status with UA, it'd be difficult for me to consistently take advantage of it since I will not fly Star if it's 50% cheaper on Sky Team or Alaska or Jet Blue as it would often happen.

With Hilton on the other hand, while my travel pattern would only entitle me to the useless Hhonors Silver, just paying for the credit card entitles me to the VIP status (ie, Diamond). Diamond is a very rewarding status (EL, breakfast, etc), and its bonus points add up real fast. It's a lot easier to stay loyal to Hilton than to UA for the reasons mentioned above... not to mention Hilton award stays for the right #points is a lot easier to find that UA award seats on the desired flight at the desired #miles .

I estimate that I'll end up flying ~75000 miles this year. Used to be I would've gotten something close to 75k EQM. But now I'll probably only get 30~40k, and that is split up amongst UA, DL, AS. I'm not a heavy flyer, but I'm still a frequent enough flyer and yet I'm just on the borderline of possibly attaining the lowest elite status (which will be pretty meaningless anyways) in any airline for next year. On the other hand, I almost exclusively stay at Hilton (probably ~3/4 of all hotel stays), get all the Diamond benefits, and essentially earn enough for a free night for every ~$1500 that I spend.