an open dipole is 73 Ohms, not 50.
The reason why with a Ground Plane 1/4 wave you see the radials at an angle to bring down the SWR to 1:1 or 50 Ohm.
On a car roof you see thee same, adjust length of radiator to get o a good swr.
Personally everything under 1:2 is good enough for me, or lss as 10% loss.