The headline is where the offer either lands or does not. Static type gives a visitor one chance to read it. Animated type gives you a second: motion pulls the eye back to the words that carry the promise, and holds it there long enough for the rest of the page to matter.
The elements cover the range, from a headline that types itself out to text that decodes from random characters, words that trade places or morph into one another, phrases marked the way a person would draw on them, real layered 3D type that tilts toward the visitor, and oversized lines that travel with the scroll. The ones that type or swap their text pin letter widths or lock the line width so the layout never jumps while they animate, which is the failure mode that makes most animated text look cheap.