If you are referring to the event on Mt. Hood some 28 years ago, in May of 1986, that seems to have been laid to poor leadership and a failure to as much as read the weather reports. But I see that there are many other opinions, none of which seem to have much to do with the suggested inherent danger of the campsite reservation system.
Persuasive Writing: Taking a Position
I would be much more worried about vacationers having to rush to a certain campground in order to beat others to a camping space by 10 o'clock in the morning, than about those that know when and where the have to be and don't have to be rushed about what time of the afternoon or evening they arrive.
I seldom see/hear late arrivals in campgrounds that are reservations based, but not so in popular first-come venues when I am often awakened by vehicles prowling around and then double parking in the middle of the night in someone else's campsite, as is, more often than not, the case at Joshua Tree N.P. in-park campgrounds.
When a driver has an entire family in the car, has been driving all day long and everyone is tired, knowing that a reserved space is ahead is a lot less stressful, and therefore safer, than that same driver when they have to start looking somewhere else when they find that there is no Room at the Inn.
For those of us that can luxuriate in weekday travel it's a different story, but for the RV'er that is on a weekend getaway, or even an annual vacation, having reservations can result in a safer trip for all of us on the road.
As for me, I try to avoid moving on weekends, in part because of the crush from Weekenders, I sympathize for them, they have to go back to work on Monday and I don't.