That's why Orthopods are the smartest physicians in the hospital. They have effectively convinced their colleagues that they don't don't know how to manage DM/HTN.
To opine on this a bit more seriously, I guarantee you many do know how to manage it especially after may an hour long lecture...but why? It's not in their best interest to start Lisinopril on a 50Y male coming in for a knee replacement who hasn't really seen a doctor now found to have microproteinuric DM and HTN and have their team follow that up in clinic. What if they prescribe it on DC, patient never follows up and gets admitted with a potassium of 7.2? It's kind of like why medicine still consults ID for a Staph Aureus Bacteremia even though we know the basics of inpatient care...there's a lot of things that can go wrong or be missed and outpatient follow up is critical. Also, at most high performing hospitals, there is an algorithm for management of critical surgical emergencies including hip fractures, spinal cord compression, etc. Hospital policy-makers have long decided that the workflow is to allow surgical teams to make OR plans, focus on their aspects, and allow medicine to comanage comorbidities. It's kind of like when you have a patient on medicine and there's an issue with a leaking PEG tube with abdominal distention. It's probably an easy fix and is something a PGY-1 GS resident is called to do. Is the medicine intern on call supposed to find some practical surgical trouble-shooting reference and follow their instructions or are they supposed to page surgery to take a look at it?