First, the balconies of many houses are not load-bearing. Changing it into a bedroom will inevitably cause greater pressure on the balcony and may bring security risks.
Second, it affects the lighting of the house. After being converted into a bedroom, some shading must be done, so the room is not well lit.
Third, Feng Shui says that the balcony is a symbol of the future. If there is no balcony, it is self-blocking.
Fourth, the doors of the unit building are closed now, and air can only be admitted through the balcony and windows. After the balcony is changed into a bedroom, the air can't enter, and the luck at home will naturally not be too good.