About Heightmaps

Some questions I had when studying heightmaps:

.Why Unity uses Raw format for heightmaps?

.Why the last pixel of the terrain is buggy when we use potencies of 2? I understand that potencies of 2 has benefits. So why heightmaps in Unity has to be a potency of 2 plus one?

.Why Raw format is 16bit and not only 8bits?

My own answers…
.Because Raw do not have a Header.
.Because Raw format add one extra pixel
.Both formats are supported