they will never provide the companionship or connection of a human partner.
They will also not provide all the headaches and frustrations that come with human relationships.
Real human partners can be annoying, pig-headed, jealous, fastidious about certain inconsequential matters, be burdened with psychological issues from their past or religious upbringing. And that is not even taking into account the more unpleasant character traits such as greed, duplicitousness, cheating, lying, gluttony, sloth, a weakness for alcohol and so on and on.
I think you understand what I am driving at.
Humans can be fatiguing and exhausting. Sex robots should be devoid of conflicting tendencies and easy to get along with.
If such things ever truly become available, truly lifelike (sex) robots/replicants, then boy oh boy, will there ever be a real serious problem with creating and sustaining real family relationships. Who'd want to go to all the hassle and expense and heartbreak?