Brooklyn 99, showing Hitchcock and Scully’s backstory, was an important move for their characters. Michael Hitchcock and Norm Scully are known for being partners and best friends of 30 years, but their presence around the precinct has always been questionable. The two are portrayed as lazy and stupid, and they looked to always be the butt of the joke for the rest of the team. However, showing their origin story shed a new light on their work at the 99, giving their characters the depth they needed.
https://screenrant.com/brooklyn-99-hitchcock-scully-backstory-important-reason/