Hmmm.... There are a number of well-defined ways to establish speed, some of which can be readily accomplished after the fact (impact damage, video evidence, length of tire marks, witness' statements of relative speed between vehicles, collision recorder data, etc.).
Last I checked, unless you pull someone's mobile device records, the only way to determine distracted driving is to have a witness who happened to see the person looking down at a cellphone - or have an admission from the driver. It seems to me that the likelihood of citing "speed" as a provable factor is much higher than that of distracted driving.
I would also ask what counts as "speed" as being a factor. In a 70 mph zone, driving 15-20 mph over in heavy rain is almost certainly a causative factor. 2-5 MPH over in a 40 zone in clear, dry weather with little or no traffic? Technically yes it's speeding, but in reality it's irrelevant. The condition and type of the vehicle's tires matter more than the speed in this case - yet both will end up being listed as "speeding at time of collision".
Let me put this another way: When flying, the only "speed limit" that is truly a hard limit (outside of the airport pattern) is Vne, right? Everything else is dependent on the plane and conditions, not on some arbitrary limit assigned by a bureaucrat whose primary goal is to ensure the steady collection of revenue from traffic tickets.