Single sign on solutions don't work when some of the systems you sign on to are air-gapped and will never, ever, EVER be connected to any network. Other networks I access are completely separated from the greater internet. It would be useful, but single sign on would take my 25-30 passwords and shrink it to about 15.
Which would be useful but would still require me to keep track of them manually.
Try convincing the US government of that. I wish you luck (I really do). Trying to educate program security people on computers is one of the banes of my existence.
Which would be useful but would still require me to keep track of them manually.