Originally, A 64bit OS was popular in the enterprise space. Businesses were running Windows NT using 64bit. I think the first version of Windows meant for consumers that got the 64bit upgrade was a version of Windows XP Pro X64, but it was uncommon. 64bit didn’t go mainstream until Windows 7. Before that, most PC hardware upgrades didn’t have 64 bit device drivers available. Even now, 64bit isn’t a requirement most of the time. You can get 64bit versions of a lot of applications, but a lot of applications still come as 32bit only.

Here’s the start of the relevant portion of the video

Where’s the fun in that?