I'd wagger these were just excuse programs aimed at releasing regulatory pressure. Employees working on them might have put their best efforts, but they were inherently flawed and limited beyond just the "viewing" aspect.
A long time ago of my employer tried to skimp on a license and we tried those instead, just to give up after a day and buy the whole package.
They couldn't enable viewing of truly crazy files without shipping the rest of the elephant with it.
And Word users never listened when told to only share RTF files instead of DOC files, except maybe early on when dealing with how Mac and Windows version files were mutually incomprehensible (RTF was kept at feature parity and documented all the way to Word 2003, precisely as interchange format)
A lot of people didn't understand there could issues at the base level. They were exchanging files with their colleges on IT provisionned machines and didn't have to mind what they were using, on a day to day level they had no issues, it was the people "outside" that were a PITA always boyhering them.
Also biting the bullet and being on the latest version of Office with everything from Access to Outlook installed sadly covered all the bases. We worked on an intranet for a smallish company and they had web components that only worked with the specific Office DLLs installed. Took us an afternoon to figure out why it didn't work on our machines.
There have been free, no-license viewers for MS Office files since the early 00s, if not earlier.
https://support.microsoft.com/en-us/topic/supported-versions...