I think this is just different ways to handle information asymmetry. The asking side knows value of the favor to self but does not know the cost of the favor for the answering side, while the answering side knows the cost of the favor to self, but not value of it for the asking side.
Friendly people would accept requests for favors where both costs and values are favorable, but they do not want to be taken advantage to accept low value / high cost requests, and also do not want to be rude to refuse high value / low cost requests.
In 'ask' culture, the act of asking only implies low value of the favor, so people are free to ask and free to refuse.
In 'guess' culture, the act of asking implies high value of the favor, so people have high bar for asking and high bar for refusing.
In both situations, there are ways to express higher or lower implied value of the favor (e.g., one can 'beg' instead of 'ask' to imply higher value, or one can 'express interest' instead of 'ask' to express lower value).
One could say that 'ask' / 'guess' is unfortunately named and it would be better to call it 'low ask' / 'high ask'.
Also, i am not sure if it is really a cultural/social thing, or personal/psychological thing, perhaps it is both.
Also, while above i describe it in a symmetric way, there is an important asymmetry - which side pays the mental load of deciding whether the request is appropriate. In the 'ask' culture, it is the answering side (as the asking side just asks for what they want), in the 'guess' culture, it is the asking side (as the answering side is expected to accept.).
From this point of view, it seems fair that such cost should pay the side initiating the communication.
Friendly people would accept requests for favors where both costs and values are favorable, but they do not want to be taken advantage to accept low value / high cost requests, and also do not want to be rude to refuse high value / low cost requests.
In 'ask' culture, the act of asking only implies low value of the favor, so people are free to ask and free to refuse.
In 'guess' culture, the act of asking implies high value of the favor, so people have high bar for asking and high bar for refusing.
In both situations, there are ways to express higher or lower implied value of the favor (e.g., one can 'beg' instead of 'ask' to imply higher value, or one can 'express interest' instead of 'ask' to express lower value).
One could say that 'ask' / 'guess' is unfortunately named and it would be better to call it 'low ask' / 'high ask'.
Also, i am not sure if it is really a cultural/social thing, or personal/psychological thing, perhaps it is both.