Aside from reasons you mentioned, I can imagine it being because it easily allows one to add a sudo or being habit because of it. For example:

  echo 3 | sudo tee /proc/sys/vm/drop_caches

Will allow you to write as root and

  sudo echo 3 > /proc/sys/vm/drop_caches

Will be a permission error. It executes the echo as root and the write as the user