I posted in this very thread about how the human vision differentiates between different kinds of motions and what processes are most instinctual deep in our brains. It is an interesting piece of research and one that is extremely relevant for airline pilots.
So, some of this will be repeat from my previous post.
But, the human vision is adapted to quickly and accurately discover angular movement and it's rate of motion. (Remember, most of our movements are angular - arms and legs like pendulums rotating around a "stiff" torso.) This ever touches the subject of navigation by stars.
Linear motion is discovered second, but - and this is a biiiig BUT - it is the MOTION that is discovered, not necessarily any shapes, colours or digits. This might seem unintuitive but imagine you stand on the prairie and something comes rushing towards you (linear motion). You don't wait to see what kind of predator it is, or if it is a dark blue or grey Land Rover. To notice this you need to make a concious effort to overcome the motion in order to see the license plate.
To make vital instruments in a cockpit (speed is kind of vital, right) like round dials therefore does not seem to be such a big deal. It's just a matter of programming.
If there is a huge reluctance to do so, I would suggest a speed tape someting more like the old speedmetres in old cars where you have a reference point that is absolute - ZERO km/h in the case of a car.
This design makes it easier to see where on the tape you are, generally, and if you really need to get your momentarily exact speed you could look at some fancy gadget somewhere else.
My line of thinking is that you rarely* need to know the EXACT speed. You need to know your speed is around-ish, below max Mach but above stall speed.
Vr, V2, etc are of course very familiar exceptions, but the old speed bugs will do just fine on a round dial. When in cruise the exact number is rarely used.