Acting isn't like most professions -- it's a craft where the process of aging makes it possible to plumb even greater emotional depths -- but Daniel Day-Lewis isn't like other actors. There's a John Mulaney joke from 2009 about how Donald Trump is not just a rich man, but more like what "a hobo imagines a rich man to be." It's easy to think of Daniel Day-Lewis in similar terms: His well-documented penchant for research and preparation, his knack for choosing roles that were physically and psychologically draining, and his tendency to encourage his own mythos made him what a child might imagine an actor to be. If Daniel Day-Lewis were a character, you would cast Daniel Day-Lewis to play him.
The movies themselves back up that image of an actor obsessed with the tension between the hardened exterior and soulful interior life. The woodsy glamour of Last of the Mohicans, the studied propriety of Age of Innocence, and the rugged desperation of The Crucible all show off this tendency. Even his take on Abraham Lincoln, a historical figure practically weighed down with pre-conceptions, was both oddly funny and deeply melancholy, complicating the public perception of the man. The collaborative nature of his relationships with directors like Jim Sheridan, Martin Scorsese, and Paul Thomas Anderson only adds to the mystique. Retiring early provides another layer of mystery.
For other performers, retiring far too early in a career is often interpreted as an act of either cowardice or arrogance. Why walk away from true greatness? You really don't think you can make anything else worthwhile? It's a point of view that's reflective of the underlying entitlement driving most fan-artist relationships: We always want more, more, more. For decades, Day-Lewis was virtually peerless because he provided more enigmas, more accents, more emotions, and more hairstyles than his contemporaries. (And top hats! Always with the top hats, man!)
By retiring early, he'll close off his career with a neatly executed backstitch. There will be no loose ends: No abandoned mystery projects with high-profile directors, no tossed-off cameos in prestige TV dramas, and no voice work in a Transformers movie. For other actors, it would be too tidy of an ending. For a performer as self-consciously meticulous as Daniel Day-Lewis, it's a perfect fit.