They do more damage than you think. They teach people to think that there are conspiracies by scientists to hide information from them. That leads to thinks like antivax beliefs and climate change denial. It's a subtle insidiousness, but it needs to be beaten. People need to be able to understand that it just doesn't happen.

Banal conspiracy theories are often "gateway drugs" to much more insidious ones...

https://youtu.be/JTfhYyTuT44