It's been repeatedly discussed (ad nauseam?) - I recommend checking out hnsearch.com.

I dislike MongoDB, but if I had to try to summarize objectively:

1) It is marketed very heavily, including to use cases to which it is poorly suited

2) It can be very complicated to run in production, I think because it actually wasn't originally designed to be distributed.

3) It has a history of data loss. I think this is because it generally favors performance over reliability, combined with #1 and #2

Because it's pure snake oil. If you got an old IMS hacker from the 1970s he would be appalled at just how primitive it is, but to its cult-like followers it is cutting edge tech and they won't shut up about it.

I have run it in production, thrown over the fence by some dumb devs who believed the lies that "you don't need a DBA". Well you need a full time team and a lot of hardware, and that's comparing it to Oracle.

MongoDB has been marketed as something it is not ,that's why.