Are you sure about that?
There are a great number of areas where your assertion "if the projections show it won't make more money, they won't do it" is false. Though somewhat flawed, the example of the legalisation of cannabis is a great example. The arguments put forward by the fanatics and Christian fundamentalists have long been soundly refuted by both economics and science (no, I don't think the former is a subset of the latter but that's another story). Two US states have finally bitten the bullet but with the pressures from the fundamentalists and the distortions that are brought in with it being so restricted (think Amsterdam), it wouldn't surprise me if these states have considerable difficulties.
Fact 1. The active ingredients in cannabis are far less addictive and far less dangerous than either alcohol or nicotine. A very major study has just been completed in Europe (maybe just in France, can't remember) that suggested that people under the age of 22 should completely abstain or risk suffering brain development problems. I heard an interview with one of the authors, the interviewer asked "So that means young people should stick to alcohol and if they must smoke then they should wait?", "Absolutely not! Alcohol is far worse than cannabis for brain development. Sustained, daily cannabis abuse in the teenage years can lead to cognitive impairment. However, even occasional binge drinking can have a much worse effect as alcohol actually destroys important brain cells whereas cannabis just impairs optimal development". The physical addiction factor of cannabis is actually very low (it's very difficult to become physically addicted, though admittedly the physical part is almost never the major one), and something like 95% (sorry, no ref for that) of government sponsored medical studies, from EVERYWHERE throughout the world, has recommended some level of tolerance/non-prosecution. Prohibition is the main root cause of even health-related issues and impedes proper treatment in many cases where the drug is actually being abused (as opposed to relatively harmless occasional use).
Fact 2. Many police departments around the world have been recommending for decades that cannabis be decriminalised. The "gateway drug" fallacy is completely based on association. If you force cannabis into the underworld, then you force users into the underworld. Just like in every Walmart and showroom around the world, the salespeople do cross-selling and up-selling. In some places cannabis prohibition enforcement is a substantial cost for police forces and almost all would much rather spend that money fighting actual crime. Legalisation means quality control and (slightly) more control over the use by the younger age groups.
Fact 3. The tax revenues that could be generated (as shown by the Californian study that prompted the referendum) by legalising and then taxing are huge.
So what do we have? A situation where basically all evidence: economic, scientific (health), and even your friendly local Bob say that cannabis prohibition is hugely expensive and is actually counter-productive - i.e., the prohibition of cannabis is far worse for individuals and even society as a whole and yet it is still the status quo in the vast majority of regions and states throughout the world.
Take home point:
Superstitions and punishment disorders can trump science, economics and logic - DRM is just such another case of people trying to cling to a fundamentally broken way of doing things, just like you see in many other areas of our lives...