1) The middle class is dying. Less income. Less free time.
2) Americans are less fit and healthy than before and require more comforts while camping. More comforts means more costs which does not work well with less income. Many need generators and inverters to power their 5 TVs, dual A/C's, wifi-hotspots, satellite receivers, cell phones, computers, etc.
3) Most kids prefer a virtual world rather than an uncomfortable real world. No wifi or cell coverage is catastropic.
Camping seems to be less and less getting away from it all and has become more like bringing it all with you, which has made it more expensive.
I saw a video of a father taking his two kids out camping. Both kids were inside the trailer on the couch in the dark playing with their tablets / smartphones / portable game systems. The trailer was parked next to a lake in the woods.