[davak]

Zillions of reasons. If you miss your meds, that stent can abruptly occlude and cause death. Maybe you open one large vessel but the downstream vessels are clogged—even microscopically. Place enough useless stents and you’ll hurt patients from dye, bleeding, infection, etc.

On the other hand, studies of procedures are done on very narrow patient populations. Our patients often don’t fit into those perfect boxes. What’s “needless” is difficult. As long as folks get paid per procedure, it adds bias that favors doing instead of not doing.