Potential functions are derived in Conservative fields, Conservative fields are fields in which the line integral is path independent. meaning if I were to go from point a to point b, the amount of work I would have to do against the field in order to move something from a to b would be independent of the path that I take. this is crucial in defining a potential function at a point as without path independence, the whole concept is completely redundant as different work would be needed to go from the same 2 points depending on the path I take, and hence the use of potential difference between 2 points to find the amount of work done on an object, wouldn't have a fixed answer
Mathematically, You can prove that for a Conservative field, it can be written as $\nabla \phi $where $\phi$ is a scalar function,$ \nabla $acting here as the gradient operator. From the fundamental theorem of line integrals the line integral in this form would have an answer$ \phi(b) -\phi(a)$ where a and b are positions in space, which has nothing to do with the path inbetween.
Electric fields created via induction require that $ \nabla × E$ be non zero, using stokes theorem we can see that this means the E field generated is not path independent and the concept of a potential at a point breaks down due to reasons mentioned above