For the record, all of my projects use self hosted analytics.
But you have to understand, the marketing team wants analytics. You can request to allocate engineers to setup a server with motamo, which will require replication, setup, maintaince, etc.
Your project manager is going to say "Wait this is going to take X man hours, require maintenance, etc? Why don't we just use GA like everyone does, like we always have, as it's free, has builtin redundancy, requires no maintaince, and can be added in 5 minutes?"
They aren't going to even think about privacy. Most consumers don't even care (although they should).
To answer your question though: Instant setup, ease of use, zero-maintance, zero-cost, and it's an industry standard. Literally the only downside is less-flexibility (mostly only applicable to programmers/power users) and privacy issues, which again, not very many consumers or companies care about this form of privacy (but again they should be).
