I got a theory from the latest page of the comic
In case of moral breakdown or any other overwhelming emotion, these bugs affect the carriers by partially erasing their memory so as not to worry about the disappearance of people.
This helps the symbiosis work better because the infected carrier travels without worrying about harming anyone, making the "hunt" easier + the normal behavior of the infected will not reveal anything abnormal about them.
And I think the bugs are not strong enough now to control the carrier constantly, that's why they carry out such actions.
Is my theory close enough lol?🤔
Perhaps! Not much else I can answer with other than "Perhaps"! Interesting theory!