Is it possible to modify the default lifecycle? How? Why?

Yes, it's possible. There are different lifecycles one can choose from. For example "create_before_destroy" which inverts the order and first creates the new resource, updates all the references from old resource to the new resource and then removes the old resource.

How to use it:

lifecycle {
  create_before_destroy = true
}

Why to use it in the first place: you might have resources that have dependency where they dependency itself is immutable (= you can't modify it hence you have to create a new one), in such case the default lifecycle won't work because you won't be able to remove the resource that has the dependency as it still references an old resource. AWS ASG + launch configurations is a good example of such use case.