In 1918 a lot of people, especially in rural areas, probably died before they even had a chance to see a doctor. A rural person could easily be a day's travel or more by horse drawn wagon away from a doctor.
It might take two people to take the sick person. One to handle the horse and wagon, and one to tend to the sick person. Having two healthy people away from work for several days, and having the wagon unavailable for that time, could be a serious hardship.
I'd thus expect such people to tend to wait until it was clear that what they had was more serious than any normal flu they had had before. News traveled much slower in 1918, especially in rural areas, so they might not know that there is an unusually deadly flu pandemic in progress.
So by the time they realize that they are going to need help, it might be logistically too late.
Even if our medical treatment was no better today than in 1918, we'd probably save a lot more just because news spreads faster and more widely, we have faster transportation, and we have faster communication.