This keeps coming up every time there is "perceived" shortage of capacity.

TSMC dont have capacity problem. They are very much willing to built Fabs if their customers are committed to it. But no company other than Apple has ever done that. AMD could have place a large order over the course of the year. Basically a bet that they will sell that many chips. And TSMC will adjust or built accordingly. That problem is no company is willing to place that bet. What if they dont sell and stuck with big pile of chips?

This is simple Supply Chain Management, it is the same principle in every other industry.

Because outside of very specific cases like solar panels, display and LEDs spinning up new fabs seems to be quite risky the investment costs is huge and it seems that TSMC is very much content to make major bucks with fewer customers that are chasing the latest and greatest node.

The more fabs they have the slower their node progression will be and the cost of each new node these days seems to be almost exponential.