Look what happened when he did, there's your answer. He knew what their reaction would be, so he put it off.
"They never tried" because they're friggin doctors. They knew what was going on with her body and its control mechanisms, so no, they didnt try, they knew she couldn't swallow.
No I am not a doctor, but this is something I'm very familiar with because I was involved in the exact same situation with my grandmother after her stroke. Lucky for her, she was able to communicate her wishes through a series of whisps and nods, she didnt want the tube. It wasn't easy, and my aunt tried to fight it, but in the end it couldn't be denied that it was for the best.
And yes, drowning is less apealing hten starving. It's painful, it sends you into convulsions and your body tried to fight it, have you ever inhaled water? Starving, on th eother hand, is a much more peacefull way to go. you feel nothing, especialy if medicated. You eventualy fall asleep and never wake up.
There's too many people tryingto get involved in this that have no fucking clue what is going on. If you're a person of faith, why would you have a problem with her shuffling loose the mortal coil?