I guess they're less of a thing now because it's been done so much, and with Internet everyone is immediately aware of it, they're not as fun as in the past.
Android for example had multiple easter eggs, when you go the phone information and tap multiple times on the version number you get an animation.
I wrote Task Manager and I just remembered something... https://www.reddit.com/r/techsupport/comments/gqb915/i_wrote...
AMA: https://www.reddit.com/r/IAmA/comments/kfpjhg/i_am_dave_plum...
I can, yes. Easter eggs aren't some clever thing that a developer sneakily included. They're just features that aren't documented. They go through planning, dev, QA, etc like everything else.
And the product owner agrees spending half of the sprint points on Easter eggs. :)
I'm not sure Microsoft did formal code review at the time, by the way. Windows was the first time its rather informal development practices became a liability.
Easter eggs are still a thing, in software and even in production cars.