A living thing has to remain viable at every time step, even intermediately.

While growing it has to be viable at each step.

Or in evolution, each intermediate adaptation also has to be useful enough to be maintained.

A path from there to there that is continuously viable.

Built things don't necessarily need that.

But a built thing will erode; it needs living things to decide to invest in, who find it useful.

And if you built a thing, you don't know if you'll find enough other things that want to invest in it.

Whereas a living thing, that has been living at every intermediate step, is known to be viable by the fact that it continues to exist.