Forklifts probably don't have speedometers because forklift operation depends on the load, travel conditions, and other variable factors. There is no universal safe forklift speed.

The use of a speedometer would also be more of a hazard than a safeguard as it would take the operator's focus off the path of travel where it belongs. A lot of forklift travel is also in reverse where a dash mounted speedometer would be worthless.