I think it's because the early marketing and hype compared NoSQL to rdbms. At the beginning they were all "hey man, don't schemas suck? Isn't it a pain having to migrate your data? Sometimes you just wanna cram shit somewhere, go fast, break things, and your DBA is a jackass! MongoDB"

And people, at that time, were either like "what the fuck?" and continue to not trust it to this day, or "hell yeah brother!" and then put everything into Mongo and were surprised when it lost some data or got into a corrupted state, or at least were surprised the first time they thought "huh, I really wish there was some consistency to all this data..."

So yeah, I think MongoDB didn't come into the scene as "I'm a new kinda thing that has niche uses" it came on as "hey pussy, why are you still using your dad's DB. Are you afraid?" and people still carry that in their hearts