I don't think this is as simple as a google search. This isn't a regular business, and it would be nice to get a HN-user-vetted answer on a retreat that doesn't try to upsell you, and offers the "right" daily events.
No, not 'why can't you just google it'. The question is why can't you just DO it. Take some food in to your room, put your devices outside, close your door.
I imagine for the same reasons they can't "just" quit smoking, lose weight, get in shape, write a novel, etc. They may not believe they're capable, they need support, they need structure, they need incentive, etc.