And all of them had a thing where if you tap them, they stop working until they get untapped.
And SOMEHOW, Howling Mine and Winter Orb SPECIFICALLY retain this clause, and no others, not even Meekstone on which it would probably be very relevant, do.

Also Static Orb apparently, even though it has never used the Continuous subtype (see the difference between 7ED and Tempest versions).

Does anyone with better understanding of MtG R&D history know why these three have this clause?

As for why Static Orb got the change despite not having "Continuous" I think the rules change was 6th edition so any artifact printed before that and then reprinted in/soon after 6th edition would be a candidate for the clause. I don't know who decided that meekstone didn't need it.

The change happened in Sixth Edition, so Static Orb worked that way even though it was never printed with "Continuous" on it.

My understanding of the situation is when they made the change in Sixth Edition, they originally wanted to preserve the original functionality for the cards that they had actually reprinted, which were Howling Mine and Static Orb. I believe the other formerly continuous artifacts had similar Oracle changes but the changes were never enshrined in an actual printing. Later, they decided to fall the other way when it came to preserving function vs preserving the printed text, so they reversed the errata changes for all cards except the cards that were already printed with the new text.

This is similar to how when lifelink was introduced on Mistmeadow Skulk and Daybreak Coronet, it was a triggered ability like on Zebra Unicorn and Loxodon Warhammer. Those other cards got updated to have lifelink and the Warhammer got printed as such. But then lifelink changed to a static ability, so the cards that gained lifelink lost it again, except Loxodon Warhammer was already printed with lifelink on it, so it got to keep it.

I'm not sure how Winter Orb fits in here because it doesn't look like it got reprinted until it was put in MODO years later.

I think Winter Orb got to keep it because that functionality was key to its use in Prison decks at the time, so changing the rules for it would be clear functional errata that affected how the card was actually being used.

I have the same question about MtG R&D history bro.

As neru pointed out, in the great 6th edition rules overhaul (April 1999), they updated the functionality of continuous artifacts. They issued three cards errata to keep the common functionality of these cards in popular decks. (The other continuous artifacts weren't really played that way.) In May of 2011, WOTC had an Oracle update focused on matching printed card text. At this point, the most recent printing of Howling Mine (M10) and Static Orb (7th Edition) had been reprinted with the "As long as untapped" clause. Winter Orb, however, had no such clause printed in any edition. So at that point, Winter Orb could no longer be shut down by becoming tapped. Then in June of 2016, they released Eternal Masters, and with it, decided that Winter Orb was a more interesting card with the shut-off functionality. So they took that opportunity to errata the card once again, printing a new edition to cement the functionality. (As much as anything is cemented in MTG, that is.)

And there you have the awkward tale of how Winter Orb went from being a Continuous Artifact to a Shut-Down Artifact to a Stand-It's-Ground Artifact to the Artifact you know and love today. (Note: I spent way longer researching this than I should have. Sources include multiple WOTC articles, magicsalvation, tappedout, askajudge, old reddit posts, and other places I've long since clicked into non-existence.)

I'll reiterate razorbornes answer that actual decks used these cards and cared about tapping them to turn them off at the time that the continuous artifact rules baggage was being chased out.

It sounds like you're referring to a specific context in a trading card game, possibly Magic: The Gathering, where certain decks utilized cards that could be tapped to turn off continuous effects, especially during a time when the rules regarding artifacts were evolving.

these new spambots are kind of creepy