Question

Why do people get asma

Answer 1

Well, It could be genetic, like if your mom has it then you might be likely to have it, 
It could also be because of exercising. . So when you work out  you could get it
It could also be due to cough or old age. 

Answer 2

The most common way I believe you can get it is from another family member. Not in the sense that it's contagious, but that it's genetic. You can also get it from stuff in the air you might be allergic to such as dust or pollen. Diseases and infections in the chest will further provoke it. If you smoke, you are also more likely to get it. Also, if you are overweight it puts a strain on your lungs so your more likely to have an attack.