Using a finite support iteration $\langle P_\alpha, \dot{Q}_\alpha : \alpha < \kappa\rangle$ it has been shown that if $\kappa$ has uncountable cofinality, then using Mathias forcing one obtains a mad family of cardinality $\kappa$.
Question 1: Why exactly can't we use this same approach in the case where $cf(\kappa)$ is countable?
Question 2: If finite support iteration for some reason breaks down, could we perhaps instead use countable support iteration?
Thanks for your help!