It's a sunk cost thing. Someone who has spent large quantities of money (even for small values of large), may not feel well but still feel that they need to go into the park because they've already paid for it. If the alternative is laying in bed feeling bad while already having paid for the park vs slowing moving through some of the park while feeling bad to get at least some value from the money already spent.It's hard for me to believe anyone running a temp of 100.4 would be asymptomatic and feel like spending a day walking ten miles at a theme park. I guess anything is possible.
The temp check by itself is definitely a last ditch check, and not going to catch much. Probably something, but not much. I think, it's mostly theater. It'll probably catch some small percentage, and may catch other sick people who probably shouldn't be there either. Emphasis on the "may".
By that measure, we could lift all restrictions and the death rate would still not go high enough to threaten the survival of our society.
Only for some definitions of "survival of our society". The economy would collapse. With no controls at all in place and a million dead, people would stop doing all kinds of things. More people than currently don't do them with the restrictions in place.