For more than a decade, Guy Shoemaker pitched military service to potential new recruits with one key promise: healthcare for life. “You’re going to have medical and dental for the rest of your life,” said Shoemaker, a retired Army sergeant first class and recruiter who spent a year in Afghanistan. “I used that phrase too many times.” That promise held up when Shoemaker, 64, of Fort Worth, Texas, was diagnosed with throat cancer in 2021. TRICARE — the military’s healthcare program for active service members, retirees and their families — covered the chemotherapy, radiation and years of follow-up care that...