In my job as an Austin Home Inspector, I am frequently finding rotting door jambs due to water absorption on exterior doorways.
The aluminum thresholds collect water and allow the adjacent wood door trim to absorb it leading to wood rot. This rot then migrates into the door itself and also to the wooden floor decking if so constructed. I photograph this area for all my customers and add a "preventative maintenance recommended" blurb in the report to inform them of this potential. A nickel's worth of silicone along this joint can save LOTS of time and potentially money. All that is needed is for a bead of silicone along this joint, from front to back to keep the water away from the unpainted hidden wood!
So, don't forget to add this to your report!
Home Inspector Austin TX