A Denver Center Controller reported Denver TRACON would not approve direct routing to destination for a Medevac flight requesting priority handling. The Center Controller reported this is a recurring issue and TRACON policy.

Narrative

Aircraft X was direct ZZZ4 coming from ZZZ2 sector 5 and PVD'd (pointed out) the aircraft to sector 13 to coordinate the direct routing. Once I received communication with the pilot I checked on the urgency of the Medevac status and the pilot stated it was the most urgent situation needing direct so I relayed this information to sector 13. Sector 13 called me back and stated that D01 (Denver TRACON) denied the direct routing. I issued the LOA routing; (ZZZZZ.VX.ZZZ3.ZZZ4) and let my Supervisor on duty know that the aircraft had been denied direct ZZZ4 and that their situation was urgent. No change was allowed for the Medevac. The pilot gave the doctor's name and phone number and stated he hasn't had a more urgent situation and needed direct. I calculated the miles and it was approximately 30 extra miles the Aircraft X would fly. Please help with these. This is one in more than 10 medevacs that I have worked in the last couple months that have been denied direct routing from Denver TRACON (D01). Every one has been denied. Our ATM (Air Traffic Manager) has now even backed D01 and put out a memo that we are to follow the LOA routings on Medevacs. I recommend that we allow these aircraft to go direct. This is the first one that I have submitted just because of how urgent this one was.