The Japanese may be forgetting how to write kanji ("Japanese survey on forgetting how to write kanji"), but, so far as their signatures are concerned, perhaps they don't really need to write them anyway, since they still rely heavily on seals for affixing their John Hancock to documents. When I lived in Japan (around 1995), even I had to purchase a seal, or I wouldn't have been able to get properly registered as a resident alien.
Once, in connection with some artifacts from China, I asked the Director of the archeological institute who was going to give them to me if he could prepare a certificate stating that I had the right to submit them to C14 and other types of analysis. He said he'd be happy to provide such a certificate, but that his institute had undergone a reorganization and renaming, and he was waiting for a new seal. So I waited patiently for the certificate, but the seal just kept getting delayed. Finally, when it came to the point that I desperately needed the certificate right away, I told the Director just to send it to me with his signature affixed. He laughed and said to me that such a certificate was worthless, since his signature meant nothing, whereas the seal meant everything. But I told him that, in the West, his signature meant everything and the seal meant nothing. He finally yielded to my entreaties and sent the certificate with his signature, experiencing a shock upon learning that his signature was more important to me than the seal of his institute.
I've had this sort of thing happen to me many times in China and Japan. And something similar happened recently to an American expat in Taiwan. I sent him a check as a contribution to a cause we both believe in. He wrote back:
I deposited it yesterday, which turned into an ordeal when the people at the bank said that my signature wasn't right.
I noted, "It's my signature. How can it not be right?"
"It needs to look more like a printed version so people can read it," the cashier replied.
"But then it could be anyone who signed it. This is supposed to be *my* signature, and that's what it looks like."
They were afraid the bank in America would reject the check because of the signature. So they were about to use white-out to remove my signature so I could do it again — at which point I reacted with alarm and told them that if they tried to white out the authorization section of a check it probably would be rejected — and that then it would be their fault.
On and on like that for nearly an *hour*.
It's times like that I miss America.
On the other hand, I've also had banks here be especially accommodating to me. For example, during my first year in Taiwan I worked for an organization that issued paychecks, which is uncommon relative to direct deposit or even payment in cash. But this tradition-bound organization insisted upon issuing paychecks to me using my Mandarin* name (in Hanzi, of course). The first time I went to deposit a check in my banking account I had *no* official identification bearing that name, which has only a vague resemblance to the pronunciation of my Western family name.
"Really, it's me," I would say, trying my best to look innocent.
And they believed me and deposited the check.
Of course, I should have added my Mandarin name to my account then and there. But I forgot. So I had to go through the same thing the following month — fortunately with the same result.
So although my signature has been regarded as improper, despite documentation and, well, logic, I have also had the good fortune to be trusted to be the same person as someone who was identified only by a Chinese name.
Of course, what my friend experienced at his bank in Taiwan (not writing his own signature properly) is different from the problem of seal vs. signature that I described above, yet it also reveals what seems to be an emphasis on form over function in sinographic cultures.
My recollection from the years I lived in Taiwan (1970-72) is that seals were still very important then, and I had to use mine to take care of a lot of official business. Whether that was a holdover from the days of the Japanese empire or whether seals were also very important in Republican China when it was on the mainland, I do not know.