The standard training setup assumes data are drawn i.i.d. from a fixed distribution and that the model may revisit all of it. Continual learning drops both assumptions: data arrive as a stream, the distribution shifts, and revisiting earlier data is limited or impossible.
The difficulty is usually stated as the stability–plasticity dilemma. A system stable enough to retain old competence is too rigid to acquire new competence; one plastic enough to learn quickly overwrites what it had. Every mitigation for catastrophic forgetting is a particular point on that trade-off, not an escape from it.
Why it is load bearing for GPAI
A general-purpose system that cannot accumulate is a system whose competence is fixed at the moment of training. In-context learning gives the appearance of accumulation within a session and none across sessions. Until that gap closes, “general-purpose” describes breadth only.