[macNchz]

I've generally assumed the simplest explanation is that many of these weakly-supported procedures are regular, consistent income streams for the people who perform them in the US: my four wisdom teeth (that were causing me serious issues at age 19) cost $2k to remove nearly 20 years ago, and I know colonoscopies are billed to insurance in the thousands. There's not much incentive to move to cheaper tests or wait-and-see, when you can just do it to everyone who reaches a certain age by default.

Presumably flu shots are good business for the manufacturers, though I'm not sure about the science. After having the flu as a healthy late-twenty-something a while ago, which was...intensely horrible, I've chosen to get it ever since.

[kalleboo]

It's not always true though. My dentist in Europe pushed me to get my wisdom teeth removed early "because you're going to need to get them removed eventually anyway" at a government clinic with no profit incentive.