Why Are Viruses Not Considered To Be Alive?

I don't know where you picked up your information about viruses being dead, but allow me to disabuse you of that fallacy, Viruses are very much alive, they grow, they mutate, then mutate again, and again and again, that is why every year their is a new Flu shot... Now, a flu shot is a virus AND that virus is non-living, and the reason is so that the Doctor isn't pumping you full of living virus that can make you sicker than you were before hand. The body uses these antigens (vaccine's virus particles) as a template to create
the right antibodies, that will have the right pattern to match and know
how to destroy those same viruses in the wild (normal strength), if
they enter the body in the future to try to use our cells to replicate
themselves. Our bodies remember each virus pattern that is in the
vaccinations so that they can make those matching cells to protect us
again from that same specific flu strain (or sometimes strains that are
very similar).

Many are alive and thriving in diseases in people.  The ones that are used to inoculate people from the flu and such are dead.