Can you give some examples of the formats you'e talking about here? I'm honestly surprised by this.
The most obvious examples would be the stuff I did on my Apple IIe on 5" floppies. Obviously, the tech has come so far that you'd naturally expect the hardware to be obsolete. That also means that, but for the stuff I printed up (long before 5" floppies were supplanted by 3.5" floppies), all of that data is gone.
Now, of course, most computers don't even have 3.5" slots. Of course my 120MB optical data disks and Zip drives were also handy...until they, too, became obsolete. I'm fortunate that I have access to an old computer to read some of those files...
The next wave of hardware obsolecense left me with data trapped on those 3.5" floppies- some of which were placed further out of reach by being compressed. The programs that compressed them haven't been functional since 2000 or so, and modern compression programs can't understand them.
In addition, I had a Champions spreadsheet & campaign writeup + some work files done in Microsoft programs that were available for both PCs and Macs (my platform of choice). At one point, Microsoft decided that they were changing the way they were doing both their WP and spreadsheets...which coincided with a Mac OS upgrade that made the older programs malfunction. Being forced to run the new programs wasn't bad- they worked just fine, after all- but the problem was that there was now no way to get the old data. We even contacted Microsoft directly: they had no way for the new programs to open/read the data in the old ones, and there were to be no future updates of the older programs- they were dead. I had to pay a data recovery service to get my work files- I didn't have the disposable cash to get the gaming data.
And even though the service did fine work, some of the data wasn't in a form usable by the new programs- they were just readable on the screen. I had to transfer the data manually with cut & paste operations...LOTS of them.
Even staying within the Win/Tel world, my father had to use that same data recovery service to recover & transfer data from one proprietary medical practice hardware/software system into another when the first one went out of business.
I'm wondering what will happen if the patient records he had reduced to digital format wind up in the same situation.
In 2004, I was near the end of completing a Masters Program and doing a project in which the group I was in made extensive use of Microsoft Word and Power Point. I rarely encounter issues with these programs sharing data across platforms, but I noticed that I was getting lines of gibberish in files from one teammate in particular. Initially, I thought it was a Mac/PC thing, but it was actually an
edition thing. As it turns out, when she included data from another particular teammate and opened it in her computer (running the most recent version of Word), then sent it to me, we'd get "transmissions from Mars." If, however, the data was transmitted to me
then her, there were no issues at all. She and I could send stuff back & forth without error. It was only when the order was Old PC Word=> New PC Word => Mac Word that there was any issue at all- changing our team's editing sequence to Old PC Word => Mac Word => New PC Word or New PC Word => Mac Word => Old PC Word eliminated the problem.