Also, you complicate locking down access to the database. A reporting database can typically contain less sensitive info, reporting would not have password (hashes) for user accounts for example.
Reading other comments Brent’s made here, I’m not so sure.
No no, it's not a good idea, but it's just the reality that I usually have to deal with. I wish I could lay down rules like "no analyst ever gets the rights to query the database directly," but all it takes is one analyst to be buddy-buddy with the company owner, and produce a few reports that have really high business value, and then next thing you know, that analyst has sysadmin rights to every database, and anybody who tries to be a barrier to that analyst's success is "slowing the business down."
I work on a monolith that does this, but its usually not even necessary a single db server on modern hardware with proper resource governing can handle quite a bit.
Just because a lot of businesses do it, doesn’t mean it’s a good idea. A lot of businesses don’t do source control of any kind, so should we all do that too?
Uhh, yep, that's exactly how a lot of businesses work.
There are defenses at the database layer. For example, in Microsoft SQL Server, we've got Resource Governor which lets you cap how much CPU/memory/etc that any one department or user can get.