Alaska is effectively a one-party state. At the federal level, you almost always need compromise to clear a filibuster, and it's easier to find compromise if you can draw on more subjects. Maybe the Democrats get cheaper health care while the Republicans get a giant bust of Trump installed on the former site of the Lincoln memorial. Neither measure would pass in isolation, but together they might.
So they could agree to pass two bills. This would require the two "sides" to trust each other, but it could (ideally would) also function to build trust, which would be a good thing.
Assuming there was enough trust to "guarantee" that one bill would pass right after the other, then what's the point of having the single subject rule in the first place? Sounds like you still have riders but with extra steps (and an opportunity to betray trust).
Because it becomes harder to "hide" things - like, the provisions being bargained for, or politicians' actual convictions about particular measures. There are items which now get passed in omnibus bills, bargained for behind closed doors by leadership, which couldn't (whip votes as ye may) be passed in up-or-down votes on their own merits. Those are, in my opinion, corrupt bargains, and shouldn't happen. I like legislative horse-trading - it's an important part of the democratic process - but I'd like it to be open and above board.
You say that like everybody that is in one party agrees on everything. That is absolutely false.
It is also an inaccurate portrayal of Alaska state politics. While historically the State Legislature has been majority republican it has been more even since 2015ish. Which is coincidentally when weed was made legal.
Of course you don't have to agree on everything, but the whole point of joining a party is to coordinate action to maximize power. Whether you agree with the party policies doesn't matter if you vote for them anyway to gain political currency with your party that you can hopefully spend later on your own priorities.
That said, I guess the Alaska legislature is a lot more balanced than I assumed. If the single subject rule works there, bravo. Congress is a different beast, though.
The biggest benefit of single subject bills is that it is infinitely easier for citizens to understand what is being passed and hold legislators to account on the next election if necessary.
It makes things like the Patriot Act and Inflation Reduction Act impossible.
