Only because the specific companies you were dealing with allowed it. Unraid has a very clear policy, and the work involved to change that policy in a way that protects both users and Limetech is not trivial.
Since Limetech doesn't charge for upgrades, and licenses I got 10+ years ago are still valid, it's not fair to expect them to allow unlimited transfers for free. I'd like Limetech to make as much money as they need to for continued development. They set the prices and policies, and they've been extremely generous over the years. I think it's perfectly fair to expect new users to get a new license.
There is nothing keeping you from allowing someone else to use your license if you so choose, with or without the accompanying hardware, but any relationship with Limetech stays with the original purchaser. If you wanted to, you could continue to provide paid support to your buyer on your own time and deal with Limetech on their behalf. Limetech doesn't keep people from charging independently for support of Unraid. As a matter of fact, initially you can purchase a license for the express purpose of reselling it, and assign the license to someone else. Once the license is assigned, it stays there permanently.