Because people want to buy those things badly enough that they will spend less on housing, to a point, to afford them.
Theoretically a nationwide increase in discretionary income could create new classes of goods that would be desired enough to compete with rent and phones. Or it might not and people would just spend more on rent and phones up to their new limit. Phones would probably move upmarket to capture this revenue as they are essentially globally competitive. Rent would not as much due to the nature of housing supply and the effort of moving cities.
Theoretically a nationwide increase in discretionary income could create new classes of goods that would be desired enough to compete with rent and phones. Or it might not and people would just spend more on rent and phones up to their new limit. Phones would probably move upmarket to capture this revenue as they are essentially globally competitive. Rent would not as much due to the nature of housing supply and the effort of moving cities.