Building question : How do they decided where the outlets where be placed ?

The electrical code states the maximum distance between outlets. The architect may specify these things. Otherwise, the electrician might decide. These decisions are generally made by men who are good at building things but perhaps not as skilled at making things intuitively functional, or the ones who actually "live" in houses.

Why, have you noticed this?

not more then 8 feet apart and/or each wall. They don't want you to use extension cords and having cords under the rugs to cross a room.