It comes down to control and immutability. I know not everyone agrees with this but I believe it's fundamental.

You can use the "Immer" syntax of setState if you want:

setState(s => { s.list.push(data); });

But in some cases it is more expensive. Like a splice will per row will trigger the proxy to tell you they've all shifted a position. Where as just setting the array only hits the proxy once. Sure Solid batches the updates from the call but it's still unnecessary tracking. Solid lazily decides whether state should be made into a reactive atom based on whether it is referenced in a tracking scope.