Only because you literally refuse to do it any other way. You could easily just create an SL account, and link it to your Pass account. You do understand that all your Pass aliases are just SimpleLogin aliases, right? This is why they are built to function together.
If you actually took advantage of both parts of the product you pay for you could…
link your pass+ account to SL → Manage those alias’ in SL → buy new Pass+ sub on black friday for cheaper then re-upping current sub → unlink old pass+ from SL (SL will still have all aliases you created until that point) → link new Pass+ to SL.
You would still have all of your alias’ and they would then show up in your new Pass+ account. It takes longer for me to type out how to do this, then it does to actually do it.
It seems silly that this isnt practical for you but you were also advocating having 3 separate subscriptions.
My option costs way less and is objectively easier. Even if you wanted to just stick with your Mail+ account, it would still save money rotating your Pass+ and whatever other subs you have each year. It seems you are opposed to anything that isn’t the exact way you already do it.
read the links. I am not fighting you over a fact.