Han was full-time rebel in ESB. Why should ROTJ be responsible for showing something that happened between ANH and ESB.
No he wasn’t.
He did not hold rank within the Alliance, nor is he under contract to them. This is evidenced by the folowing:
- He is just addressed as “Sir”, “Solo” or “Captain Solo” (as he is the Captain of the Falcon);
- Rieekan refers to him as a “fighter” not a ‘soldier’;
- When he addresses the last transport on which Leia was supposed to evacuate, he says “This is Solo”, again not referring to any rank or call sign which he would have as a commissioned rebel; and, most notably,
- He gets into the famous argument with Leia about the fact that he’s decided to leave them, more or less on a whim (and the looming threat of Jabba) - something which he would not be able to do (nor need to) if he had signed on with the Rebel Alliance.
- Luke, by contrast is referred to as “Commander [Skywalker]” almost exclusively during the Hoth sequence (outside of by his friends of course).
Your arguments really don’t have much to do with our character-wise discussion. First of all, being a rebel is all about personally fighting for the cause. It is not about holding some rank. In addition, there are many other ways to support the cause than militarily (for example: politically, diplomatically, logistically, etc.), therefore one does not really require a rank to be a rebel. A “fighter” is much more relate-able term to a “rebel” than a “soldier” is. Assuming Solo was relatively famous among the rebels, it is completely normal for him to just say “This is Solo”. It would be like Che Guevara saying “This is Che” over the radio.
So the fact that he decided to stay with the rebels and help the cause makes him a full-time rebel. We know it wasn’t about the money otherwise he would be on his way to the beach with all the money while Luke was shot down by Vader in ANH. Instead he took completely unnecessary risk and joined the battle. The reason to decide to pay off Jabba is only logical as practically no one is safe when being hunted by galaxy’s best bounty hunters. So why don’t you instead complain about why ESB did not explain his very personal decision at the end of ANH? Why would ROTJ have to explain something completely technical as getting some rank.