Yeah, I was a little hesitant to suggest that this was caused by Microsoft given that. I actually agree that this problem is caused by user agent sniffing. I could see someone arguing the other way, though.
Ultimately, I think it's still on-topic because, at any point, any of these browser vendors (admittedly, not limited to Microsoft) could have started to work with webmasters for a standard of "feature claims" instead of "user agent claims". So a user agent can say, "I support frames," and a server can serve frames. Instead, Microsoft decided they'd just lie about it.
Switching to a system of "user agent claims" have been up to any one of the browsers, when they had a majority of marketshare, to push through. Mosaic/Netscape/IE all had a chance in the Web 1.0 world, unfortunately, none of them did.
I agree with that too, and admitted to such in my previous comment. Still, being the first practitioner of this comes with a certain responsibility for its proliferation. It's not a sole responsibility to your point, but it is primary in a way. It's a lot easier for others to decide to copy what someone else did than to decide to be the first to do it.
To the same point, Google is arguably the reason it persists today given the popularity of Chrome. Just as Microsoft is arguably the reason it started. (I suppose I could have been more careful in the phrasing of my initial comment since "is so useless" could imply both but I don't think it's particularly egregious.)
One thing I have always wondered about the story - were servers in the mid-1990s really sniffing user agents to decide what pages to send through? I remember most sites were static .html files back then.
Ultimately, I think it's still on-topic because, at any point, any of these browser vendors (admittedly, not limited to Microsoft) could have started to work with webmasters for a standard of "feature claims" instead of "user agent claims". So a user agent can say, "I support frames," and a server can serve frames. Instead, Microsoft decided they'd just lie about it.