Speakers enjoy sounding sophisticated with those they love. They hate speaking in slow, ill-formed phrases in an accented L2. The L1 sets a tone of authority with one's children, because syntactic or semantic errors are not made in front of them. The spouse's ability in English may be either very advanced or far behind the speaker's level. My wife knows no English.
Grandparents bring in a new set of relationships to maneuver.
They may see a lack of respect in the speaker's insistence on using the L2 in front of them when they do not understand it. In addition to the above reasons, code switching, loss of face, the value of silence, nonverbal signs, cultural expectations, interpretation of cues and communicative strategies, direct versus indirect styles of speaking and stating preferences, and issues of gender and gender roles are some specific areas in which possible miscommunication and a retreat back to the L1 could still occur. Teachers need to be able to see the valid communicative needs for continuing use of the L1 in the home at times. The promotion of L2 use in the home must begin with a respect for the L1 and its importance in the student's life. Encouraging L2 use in the home can be as simple as creating opportunities in the classroom for students to develop homework assignments.