its not like they know about the health risks
While the health risks had not been demonstrated rigorously, plenty of people had their suspicions. Two recent /r/AskHistorians threads have explored this topic.
https://www.reddit.com/r/AskHistorians/comments/59nygh/is_king_james_a_counterblaste_to_tobacco_1604_the/? from /u/LukeInTheSkyWith: In this thread, /u/RTarcher discusses very early (i.e., 1500s) European tobacco use. It's about more than just opposition, but it does touch on it.
https://www.reddit.com/r/AskHistorians/comments/54yk6m/there_was_a_time_when_everyone_smoked_cigarettes/? from /u/racedogg2: In this thread, /u/evie2345, /u/restricteddata, and /u/Fox_shirt_guy discuss growing awareness of the negative effects of tobacco consumption. Check 'em out.
Edited for clarity.
Does the dialogue make it clear that Eli is concerned about Will's health and not, say, spending his father's money on cigarettes?