Ok - excel for not ANN gets tricky when you have many rows (like 10^6) most of the tricky business with ANN is when you have >10^8 rows of data. Why is it that

Ok - excel for not ANN gets tricky when you have many rows (like 10^6) most of the tricky business with ANN is when you have >10^8 rows of data. Why is it that doing this with an excel type tool will be good?