Yeah there's lots of factors that go into it. Prevention is better than cure so all the emphasis is on smoking cessation.
It predominantly affects working class men, so there's a little bit of I don't know if snobbery is the right word. But certainly it doesn't have the powerful advocates that say breast cancer does where white middle class metropolitan women have mobilised brilliantly the last 20-30 years to change breast cancer survival rates from 50% to 90%
Also, the key word is "worldwide". In the west smoking has fallen, and continues to fall every year, leading to lower lung cancer rates. Most of the deaths are in the developing and 3rd world. Most of the money and the research is in the west, so lung cancer is lower down the priority list.