I don't use my thumb. It wouldn't really make sense to click and drag that way on an Apple trackpad since you don't have to reach down to the bottom. It's very easy to do using your index finger and middle finger.
Right, which is why having physical buttons where you can properly leverage the thumb and thus free up your other fingers to do only mouse movement and scrolling is better.
That makes no sense. You can't scroll and drag at the same time.
You are probably just trying to use the trackpad in the suboptimal way that you're used to using trackpads with physical buttons. When you can click anywhere, there's no reason to use your thumb in the first place, other than muscle memory.
Incidentally, as others have pointed out, there is no issue with using the thumb to press the button on an Apple trackpad if that's how you want to do it. You can "roll" it as much as you want to while clicking and dragging and it won't move the cursor.
