Engineering practice is a factor too. In Utah, for example, there is a standard sign banning compression braking (Jacobs Vehicle Systems, which manufactures jake brakes and considers the phrase "jake brake" to be something like a registered trademark, does not like prohibitory signs which use the phrase "JAKE BRAKE," so signs tend to use phrases like "ENGINE BRAKING" or "COMPRESSION BRAKING"), which is used on freeway exit ramps all over the Salt Lake City area. In California, however, the California Traffic Control Devices Committee has consistently rejected local calls for compression brake signing in situations similar to Salt Lake (i.e., freeway off-ramps in densely populated areas). This is really a difference in how willing the traffic sign policymakers are to accommodate a local concern which is more or less identical in both areas.
The argument against jake brake signing, which I agree with, is that truck drivers should not be using them in populated areas anyway because they are a noise nuisance. If the police wish to make an issue of it, they can pursue truckers under local noise ordinances and the like without the need for jake brake signing. Therefore, jake brake signs are unnecessary clutter, much like "WATCH FOR ICE" signs at bridges. For this reason you are more likely to see jake brake signs in states like Nebraska where sign message loads are poorly controlled. You will rarely see them in other states, like Kansas and California, where signs are used more sparingly.