We can drag the sun ray up and down and we will find ray #3 can be any angle.
If all the intensity of ray #3 are all equal, we would not be able to see rainbow.
But the intensity of ray #3 has a maximum value at particular angle (for red light near 42 degree).
The diagram in the simulation shows intensity of ray #3 and #4(secondary/outer and weaker rainbow) as function of angle.
There is a gap in which no ray will be refracted, so there is a region which will be darker in the space.

If we accept for horizontal sun ray, the view angle for red light will be near 42 degree (different angle for different color sun ray)
The light might enter our eye for us to see it. So all the light enter our eye with 42 degree is a cone.

If you move to a different position, you are viewing another rainbow. So the rainbow saw by different people are coming from sun ray refracted from different rain drop. (Your rainbow is for your eyes only!)

But 42 degree is for horizontal sun ray. If the sun is located at higher angle, then the angle you will find rainbow will be smaller. We will not be able to find rainbow at ground if the sun is above 42 degree (for example: at noon).
So we only find rainbow in the early morning or before sun set.