I think it's a matter of use case. Doing ad hoc data exploration on an OLTP system generally sucks the wind out of the performance. Even if you have some type of workload prioritization, isolation, and limitation, allowing data scientists and business analysts freely wandering through your production OLTP database sounds like a Bad Time.

The organization might say "Okay. Maybe you should do your ad hoc exploration on an OLAP system. Preferably our data warehouse where you can let your report run for hours and we won't see a production brownout while it's running."

So complexity of ad hoc joins in the warehouse generally can get more complex.