SARS had a mortality rate of 10 %. The flu is 0.1 %
In this case say 100 people got SAR - 10 people die Now Flu - 1000 people get that and - same net result.
Lets face it, how many got SARS in total - less than 10k How many people catch the flu each year? - millions litterly millions.
But as with most of these - it is overall health and underlying preexisting conditions that can and do skew statistics and not all countries log things to the same standard.
If you did what China is doing now to deal with flu, you'd drastically cut transmission rates.