EDIT: Changed title/description to match official terminology for redstone power. See also the newly-created counterpart for this issue:
Observers output strong power in the Java edition. In MCPE, observers only output activation power. See the attached image. I have no idea which behavior is intended, and both have their advantages and disadvantages. I wish we could have 2 different observers: an activation-power-emitting one and a strong-power-emitting one.