Now there are many medications and treatments that didn't exist back then, but there are many more children who have asthma. As a teacher I usually had at least one asthmatic kid in every class and I now know dozens of many adults who have it, too..
I've only known one person who died of asthma, but even for those with mild symptoms, asthma puts limits on their activities.
Why is it so prevalent?
Air quality is certainly a factor. The prevalence of fragrances in laundry detergents, cleaning products, etc., etc. makes those triggers of asthma attacks hard to avoid. Odor "eliminators," which fool the sense of smell and consist of chemicals themselves, are even more difficult to avoid since people don't know they are inhaling them.
I wish all people would be considerate of others who have that serious health condition and switch to unscented products.