True, but user-agent was 1996(?). By then, we weren't talking about limited mainframe storage devices.

It just baffles that someone can look at a monotonically increasing number, defined and incremented by a third party, and say "That will never be 3 digits."

I'd wager it's mostly fixed string indexes, regular expressions ("\d{2}"), and things like that. Maybe also some people with a "varchar(2)" column in the database.

A lot of software is written by junior programmers, not infrequently in a hurry. It's an easy mistake to make and if you've been bitten by it once you'll remember it, but many people have never been bitten by it.

Well, keep in mind that major version numbers used to change slowly. In the first ten years Firefox existed, it went from version 0.1 to version 5.0. At that pace, it would have taken two hundred years to hit a three-digit major version. In my opinion, browser vendors brought this upon themselves by changing what "major version" meant.

To be fair, in 1970 those 2 digits were very expensive. It was a calculated tradeoff at worst.

> To be fair, in 1970 those 2 digits were very expensive.

More than just "very expensive". Often, you were limited to exactly 80 columns for each record. If you had for instance three dates on one record, using 2 digits instead of 4 digits saved 6 columns, which is over 7% of the available space.