It could create a sense of loss and insecurity. Sasuke and Sakura are strong shinobi, so their absence might make Konoha more vulnerable to attacks. The villagers might also feel betrayed, especially if they leave without much explanation.
Perhaps Hinata leaves Konoha pregnant because she feels she doesn't fit in anymore. She may have faced discrimination or coldness from some of the villagers. So, she decides to leave and find a place where she and her baby can be accepted for who they are. She could end up in a community of outcasts where she finally finds true friendship and support.
Sasuke might initially be shocked. He has always seen Sakura as someone connected to Konoha, so her leaving would be unexpected. He could be concerned about her safety, especially if she leaves without proper preparation or protection.
One reason could be to protect Konoha from a great danger that he can only face by leaving. Maybe there's a powerful enemy who has a vendetta against Naruto but would spare Konoha if he goes far away. Another reason might be a sense of self - exile due to some event that made him feel he no longer belongs in Konoha, like a misunderstanding where the villagers turn against him again.
Perhaps he is lured away by an unknown force. In some fanfictions, there might be a mysterious character or group that tricks Naruto into leaving Konoha. They could make false promises about his parents or his true power, making him curious enough to follow them.
One reason could be to gain more power. In many fanfictions, Naruto realizes that the threats he faces are far greater than what he can handle with his current skills in Konoha. So, he decides to leave and train in a more secluded and challenging place to enhance his abilities.
In some fanfics, Naruto might leave Konoha as a child because he feels ostracized. Since he's the jinchuriki of the Nine - Tails, many villagers fear and shun him. He could get tired of the constant cold shoulders and decide to leave in search of a place where he'll be accepted.
One possible reason could be for his safety. Konoha is a well - protected village with many skilled ninja. She might believe that leaving him there would ensure he has the best chance at survival and growth as a ninja. Also, she may have some mission or obligation that forces her to leave him behind, perhaps something related to the greater good of the village or the ninja world in general.
One possible reason could be for Naruto's safety. Maybe she has to go on a dangerous mission and believes Konoha is the safest place for him. Another reason might be that she is forced by some powerful enemies who threaten Naruto's life if she doesn't leave him in Konoha.
Perhaps he would journey to the Hidden Cloud Village. There he could meet new people and learn different techniques. He might also try to bridge the gap between Konoha and the Cloud Village, starting from outside Konoha's boundaries. This would be a way for him to still work towards peace on a larger scale, but away from the restrictions he felt in Konoha.