A many great do have brakes, too. I haven't done an exhaustive survey, but I'd say I've seen more with than without.
The thing about choosing to follow the law or not is also about choosing to accept the consequences. If you get caught just by bad luck (stopped because a tail light was out or something) and a police officer notices you don't have a toad brake, you probably get an infraction ticket and go on your way.
If you hit someone - even if it's because the genius pulled out right in front of you, and that person dies, you will almost certainly lose the lawsuit when it comes out that you didn't have a toad brake (and it will come out), and run real risk of being charged with a crime, maybe even up to vehicular manslaughter. In the latter case, I would expect anyone who looked at the law, looked at the risk, and chose to go brakeless just to save a tiny amount of money and a few minutes set-up before getting on the road to just pay up in the civil suit and plead guilty in any criminal proceedings.
A toad brake will cost a thousand or two in parts and labor, depending on whether it's new or used and what type of brake it is (I bought my Even Brake used and have maybe 600 in it and some sweat equity), but at the scale of even a gas MH, that's a fairly tiny amount. It's way less than what I spent on gas this summer, even. For those at the diesel pusher income level, it's an even smaller amount.
In short, there's no rationalization that I would buy for not having a toad brake for any combination of vehicles beyond a Smart Car (or maybe a Miata, MG Midget, or something like that) behind a large DP. The law is clear, and the ethics far clearer. If I had ignored the law and the morality of the situation, I almost certainly would have been in a wreck last month. The situation wasn't my fault, but if I'd hit the person who did the stupid thing right in front of me for lack of a toad brake, that would have been. Fortunately, I had one and can tell the story as a near-miss.
To veer off topic for a moment, I saw an interesting set up on a DP going the opposite direction this summer. A big (had a tag axle) DP had a Smart Car hanging on the back. Literally. It was completely off the ground, mounted transverse to the MH, in some sort of carrier like the ones used for electric mobility scooters, only much bigger. Pretty cool, and completely removes the need for a toad brake :-) On a vehicle that large, I expect it was within GVWR, too.
JB, wife Thuy, 3 daughters, my dad, cats Lyn and Sami
2008 Fleetwood Bounder 35H/2009 Honda Odyssey toad
San Diego, California