A priori, this is a very strange assertion.

Assume that X% of companies are interested in you and you pursue Y leads to result in X% * Y offers. A large number of people will receive 0 offers and they'll be long term on the job market until they make a change to either X (job hunting strategy) or Y (pool of roles considered).

A large number of people will receive >1 offers because they're competitive in the marketplace. Only some tiny number of people will receive exactly one offer unless Y is very small.

That many people only receive one offer is more of a sign that they're not strategic in their job hunting approach (which is upstream of them not being strategic in their negotiations) and this is a fixable problem.