Exactly. My JL had an oil leak. I self diagnosed it as a rear main seal failure. The service manager said they don’t know why it’s leaking but could replace the rear main seal or “wait and see.” I asked them to replace it. That involved removing the transmission. After it was done, I asked the tech if he saw what went wrong with the seal or anything else. Response: “I just replaced like they told me to.” No curiosity like you said.Good point. And I would broaden it by saying, there aren't mechanics anymore, just parts changers.
When my Dakota blew the engine at 296,000 miles, my "mechanic" says "it has internal engine damage"; we have to replace the entire engine. OK, fine. I later asked him what had gone wrong (I was sure it was a thrown connecting rod), he did not know and apparently had no curiosity at all about it.