Why are almost all of my house's HVAC floor registers placed near exterior windows?
Yes, placing registers (or other heat sources such as radiators) near exterior windows and doors is the usual practice. This is done in order to combat cold drafts and ensure a more even temperature throughout the room. Here's a Q&amp;A on the subject from Ask This Old House:


  Window glass is the coldest part of a wall. When warm room air hits
  it, the air cools, and cool air sinks. The movement of cool air
  creates floor drafts that most people find uncomfortable. The
  placement of forced-air heat registers or baseboard heating units
  under the windows counteracts this process by sending up warm air to
  mix with the cool. The end result is that the room feels more
  comfortable.