The angle matches the angle of the trigger sear bar it mates with. All 700 triggers have that angle, & hence all 700 style cocking/sear pc's also have this angle.
More complex answer:
The why..........If the interface between the cocking pc/sear - trigger sear was not angled, it would hang fire or fail to fire. When you pull the trigger on a 700 the sear is released to move straight down only. The full striker spring tension is applied at 90 degrees to the trigger sear when the bolt is closed. If sear mating surfaces where 90 degrees to the direction the sear needs to move to fire, it would likley not move at all.
Safety is dependent on how much sear engagement there is between these to mating surfaces. If things were so out of spec that very minimal engagement/mesh was present then it would be possible that the cocking piece could slip over past the trigger sear causing an accidental discharge.
The picture below is the cocking piece from a Bergara B14R rimfire. Since this is a Rem 700 footprint action and takes 700 triggers notice the same angle as shown in OP on your 700 cocking pc.
I modified this via cutting it back to remove .070 cock on close, but I maintained the factory angle. You can see the dark wear mark on the shinny machined spot. This shows how much engagement I have with the Huber 700 trigger sear.