One of the things that causes a lot of pain is the way in which software is implemented differently by different vendors on what is supposed to be the same standard. Browsers all treat HTML differently (some more than others!). Some browsers interpret mistakes strictly, others are more tolerant. Look at OAuth and you get similar issues with inconsistency which make for headaches and development costs.
Anyway, I realised it is very easy to point the finger at others and their shortcomings without realising that we also need to work consistently! After all, the others are just people like me who work for other companies. They are probably not massively more or less strict or more or less striving for the right thing.
In other words, if we want to change the world, we need to look at the man in the mirror. Have you ever asked, for example, why some people require password changes and others don't. Some sites need a strong password, some don't care, some sites allow all manner of symbols in passwords and others only allow letters and numbers. These systems were all written by people like you and me and I suspect that rather than looking into the standard practices and copying them (or even better, using a library someone has already written!) what we do is either reiterate what we learned parrot fashion without understanding it well enough or otherwise we put ourself in the position of ultimate authority and decide what is right and wrong. Even worse, sometimes we get ordered around by our bosses who might not even understand but that is even more reason to rely on established knowledge that we can refer to rather than just arguing with our boss about what we think is right (and the boss usually wins that one!).
Anyway, if we want consistency, we must also apply consistency then perhaps one day....nope, I don't think that will ever happen.