I’m already immortal. So are you. I would have no interest in a false immortality grounded in an illusory material world.
Many people live to be the age that Dick Clark did and older - in my family, living to one’s early 80s and even into the 90s is not remarkable, even with health issues. (In fact, it’s been said that one of the best ways to live a long life is to develop a chronic health problem and take good care of it.)
Agreeing with you about the immortality of the soul.... however, the Evil Ones know their time is short, and that their souls will be judged and found wanting, and will likely not be found among the immortals of the saints in Heaven.
Because they know that, they are therefore quite interested in doing what is possible to extend their miserable earthly lives. FWIW