Nah, some speed limits are arbitrary or used for revenue generation by traffic fines. That's a proven fact. Most crashes are because of differences in speed. We have some unusually low 55mph straight highways who's engineers say can do 75 in all weather conditions.
Going with the flow of traffic is a law in many jurisdictions. And state police will pull people over for "impeding the flow of traffic" if you are cruising at 55 in the fast lane... even if that's the speed limit.
In Massachusetts, impeding the flow of traffic is a violation of the Code of Massachusetts Regulations (720 CMR) and the Massachusetts General Laws: 720 CMR 9.06(6) Drivers cannot obstruct the normal flow of traffic on a highway. If a driver is found to be in violation, they may be directed to pull over and wait for traffic to pass.