There's limited amount of lean-angle before you roll off edge of tyre and lose traction.
Here's article I saved from somewhere.
In most regular riding, staying in-line with bike will be fine. When you're riding more spiritedly, it's best to hang off inside. This gives you larger safety margin in case you come around corner and have to tighten your line for obstacles. Such as deer or potholes or gravel. Difference between max-angle of tyre and your current bike-angle is your safety factor. By dropping body inwards to raise bike, you increase reserve safety angle.
Another thing that helps is when you hit unexpected loss of traction such as gravel or water, a bike that's more upright when cornering (with you low on inside) tends to drift laterally while maintaining same lean angle. If it was leaned over more with you in-line , front tyre would just let go and you've low-sided.
Here's article I saved from somewhere.
In most regular riding, staying in-line with bike will be fine. When you're riding more spiritedly, it's best to hang off inside. This gives you larger safety margin in case you come around corner and have to tighten your line for obstacles. Such as deer or potholes or gravel. Difference between max-angle of tyre and your current bike-angle is your safety factor. By dropping body inwards to raise bike, you increase reserve safety angle.
Another thing that helps is when you hit unexpected loss of traction such as gravel or water, a bike that's more upright when cornering (with you low on inside) tends to drift laterally while maintaining same lean angle. If it was leaned over more with you in-line , front tyre would just let go and you've low-sided.