If people are cancerned about fatal disease, why does nobody proactively prevent catching the flu, given the stats of yealy deaths from influenza?

Some people do, about 20% in Saskatchewan.

I've been getting the annual flu vaccine since it became available.

I don't particularly worry about disease and accidents and definitely don't live in fear, but I take standard precautions: vaccinations, diet, fitness, PPE in my shop, etc. It's all relatively simple and mostly low effort.