A mathematician here. The problem is that both 0 and 1 are useful in different situations: when dealing with sequences and series, especially ones arising from discrete models where the important thing to consider is going from one term to the next one (as is always the case when dealing with series), or when sequences are used as discrete approximations of a continuous process, it usually makes much more sense to start indexing with zero. On the other hand, using zero indexing with matrices and vectors leads to madness.