Everyone has a threshold regarding the amount of suffering they are willing to endure rather than dying. Yours (and your grandfather's, per your other comment) may be high, but so isn't everyone else's.

Suicide and euthanasia are valid options in some situations, which are up to each individual to evaluate for themselves.

The doctor in the article has been confronted to the selfish side of love too many times. People want their family members to be kept alive because losing them would make them sad. Somehow more sad than seeing them suffer and slowly die anyways.