Why the smallest snag late in a flow ends the purchase

An e-commerce site tracked abandonment at each checkout step. A “re-enter your email” prompt at step two caused four percent abandonment; the identical prompt at step six caused nineteen percent. The effort was the same keystroke; the user’s tolerance for effort was not. A pebble became a wall when the runner had no legs left.

What everyone sees

Users describe the late-stage email prompt as “annoying” or “unnecessary.” They blame the interface rather than their own depletion. The frustration feels proportional to the inconvenience, but the inconvenience is identical at both stages — what changed is the user’s capacity to absorb it.

What is actually happening

Baumeister’s depletion model predicts that tolerance for frustration is a function of remaining self-regulatory capacity. A depleted user lacks the resources to inhibit the quit impulse that a fresh user would easily override. Luce, Bettman, and Payne’s effort-accuracy framework adds that as processing resources decline, consumers adopt increasingly effortless strategies — and the most effortless strategy of all is abandonment.

Why it stays hidden

The snag hides because it is objectively trivial. Nobody expects a single email re-entry to kill a sale. The disproportionate impact is invisible in UX audits that evaluate friction by task difficulty rather than by the user’s remaining regulatory capacity at the point of encounter.