Most people have trouble even taking a pill regularly. And that's painless. Regularly self-inflicting pain like hunger for 40+ hours at a time has absolutely no hope of becoming a standard therapy in medicine. The percentage of patient compliance would be in the single digits.
I don't even know how people fast for that long. I start getting head-aches and feel awful long before that. So just deciding to fast for 48 hours/week seems untenable to me.
Why not? I mean why reject it a priori?
Who said it will be difficult after the first few months? And what if it has beneficial properties?