Uncertainty.
Unfortunately, I doubt this will translate well to Europe, or other parts of the world, so it's an Americocentric comment. I don't know other parts of the world well enough.
1. Economic
2. Computers (technology)
3. Culture
4. Health Care
1. Although it was fading, in 1967, a career for life was the norm. Industry dependent, but job switching was far, far less common then now. The kinds of things people did as jobs had not changed too dramatically since 1927. Industry was factories and offices. There were white and blue collar jobs.
But my argument is not that the types of jobs have changed since 1967. Although that is obvious. It is that we're not certain those jobs will be done here for much longer. And we're not sure in 10 years what kind of a job they will be.
2. 1967 technology had existed for some time: TV, radio, the car, the typewriter, the printing press, the factory. And one could expect they would have a similar life beyond that point (and of course they did, for at least say a decade).
The car, for example, has become vastly more reliable and requires less maintenance then the 1967 versions. However, my point is that I'm less certain that I will have a car in, say, 10 years that even operates on the same principle (internal combustion of gasoline) then 10 years ago. I'm not certain that American car companies will be able to make a decent passenger car at that time, or even what it means to be "made" by General Motors. In '67, the parts were American. The car was assembled in America, and some parts were likely made by private contractors, they basically sold them just to GM built to GM's specs. The steel was made here, too. And the car would be crushed here.
3. Culture is less homogeneous. Which is not my central point. I can't forecast what the culture will be like, generally. Nine of ten music formats in 1967 would likely have been around in 1977. Whereas I simply don't know how many music formats will survive as commercially viable in 10 years.
A man reaching maturity in '67 likely knew where he stood in society. Take a particular person, likely to land in jail for 40 years: blue collar, southern, white male. Age 20 at the time. Think of the jobs he would have done in '67, the relative certainty those jobs held. He fished, worked in a factory, or did manual labor. And expected he could do that for some time. Now take the same type of person. Same class. Same place. What's he doing now? And how long is that going to last? Is he defined as having a place in society?
4. Medical Care is less expected. (Sorry, highly US specific) Now we could treat that well with a simple procedure - but who gets that is largely divided: some do, some don't. Whereas in '67 if you needed it, you got it and the hospital ate the cost, if necessary.
Even with insurance, it is largely unknown if the most effective treatment will be covered, or whether mortgaging the house will pay for it.
Further, I'm totally uncertain what the US system will even look like in 10 years. If we don't have socialized care, and costs continue increasing like they have for decades, exactly what fraction of the US will be covered at all?
And what, exactly, will care look like for those without insurance?