In no-deco diving to 130 even to 160' I'm quite certain the desent rate is of little consequence if you can tolerate the equalization.
I've heard some reports of enhanced narcosis from fast descent on air, but in no stop recreational depths using unassisted or FREE descents, its of little concern. Free descents depend on your buoyancy, and if a diver is weighed properly, the first 60' will be way under 60 fpm even with all the air removed from one's BC or wing.
The USN gives a rate of 75'/min but doesn't qualify why this is so.
Does anyone know?
There is a theoretical reason for limiting the descent rate, to simply make calculations for deco models possible.
http://www.decompression.org/maiken/VPM/RDPW/VPMech7/VPMech7.htm
However, practically speaking in recreational dives, its difficult to stick to a finite rate of FREE descent [as opposed to a powered descent by swimming or scooter] since its proportionate to one's buoyancy, which geometrically diminishes with every ATA of compression but braked with every breath one takes. FREE descent rates stablize depending on how many breaths one takes per minute, as each inhale causes some amount of positive buoyancy.
Free divers descend in excess of 100-300 fpm without issue, so it there is some physiologic concern, its related to breathing compressed gas.
Among the members of the AUE in S. Florida, they point their scooters DOWN and power descend, and claimed peak rates in excess of 200 fpm can be obtained. These divers do it regularly and consistently without issues. A descent video of one such dive I clocked the rate in excess of 100 fpm.
Most printed tables assume arrival at the bottom depth is instantaneous, as using a fixed descent rate that most divers likely will NOT do, puts unecessary complication in table calculations. In computer models, a fixed rate of descent can be used, and in many instances, it simply reduces one's actual bottom time or considers the dive a multilevel dive. For conservatism, many divers use instantaenous descent to calculate inert gas loading based on spending the entire bottom time at depth, not consumed by the descent. For example, a 30min at 80' means all 30' is spent at 80', even if it took 1-2minutes to descend at that depth. The presumed inert gas load is thus higher than what the diver actually experiences. Thus, there is built in conservatism in the instantaneous approach.
There is concern in rapid descents in deep dives past 300' to help limit the effects high pressure nervous syndrome. Its usually of concern around 600' at descent rates over 100 fpm. At these depths, any time spent here rapidly pushes one into inert gas saturation, so its only in saturation diving than descent rates become an issue.