Why do some artifacts require tapping and sacrificing as an activation cost?
Both forms of these kinds of abilites, with and without the tap requirement, have appeared on a significant number of cards, both recent and old. For example, compare Fountain of Renewal from M19 with Explosive Apparatus, also from M19. This implies that this is not a standard template, but rather a choice they make on a case-by-case basis.

The primary other interactions that make it relevant whether or not the artifact taps are other abilities that tap artifacts as a cost (such as Ghirapur Aether Grid), spells with Improvise, effects that make the artifact also a creature (making summoning sickness apply and allowing the artifact to attack), and effects that tap permanents. The design team probably considers these interactions when making that choice.

Cards that have been revealed so far in Thrones of Eldraine that have these kinds of interactions include Animating Faerie, Shimmer Dragon, and Workshop Elders. Of particular note, the same animation effect appears on both Animating Faerie and Workshop Elders, and may be a minor theme in the set. These cards probably affected the design of Food tokens, and of the card Witching Well, which sacrifices but does not tap in the cost of its activated ability.