A person will need a feeding tube when:

1) they CAN'T eat or drink
2) they CAN eat and drink but not effectively enough that it doesn't leak into the lungs and cause pneumonia
3) they CAN'T eat or drink enough to meet the body's need for nutrition/hydration

Our treatment protocols put us at very high risk of not being able to eat or drink at all, safely or enough.
There's no crystal ball - no MD can tell for certain who will make it without a feeding tube and who won't - whose swallow will "make it" through the duration and whose will not. For this reason, many MD's, understandably, take a conservative route and recommend a G-tube to be placed before potentially life threatening complications arise at the weakest point of a Patient's life.

The decision to opt for a feeding tube is a difficult one - the main reason to do it beforehand is to be better prepared for potential complications.

The swallow's going to make it or it isn't - it's not a matter of will power or mind over matter. It's a sophisticated and, under normal circumstances, very protected mechanism. Treatment is going to change that - we just never know to what degree.