That's because phone browsers have the insane braindead default of scaling everything into tiny unreadableness. You have to explicitly say "stupid browser, nobody ever wanted this shit, behave sensibly by including <meta name="viewport" content="width=device-width, initial-scale=1.0">. No idea why this idiotic custom still hasn't been purged from mobile browsers, but I guess it's just a valuable tradition now...

Before mobile browsers arrived, everything was fine and nobody needed meta viewport stuff. That's why this 1997 era page doesn't have it.