In short cardinal movements are important movements.
They are important developmentally speaking. All children need to develop these cardinal movements. If they are not developing particular movements that is a problem that should be addressed.
Getting to them late doesn’t matter. You can get to them late, but if you don’t get to them at all, you will not develop the neural structure required for specific activities. If you do not understand how your body moves in space the chances of you understanding how letters are arranged in space is diminished. Which is important for being able to identify and tell apart ‘b’ and ‘d’, as well as ‘p’ and ‘q’.
So not knowing that there is a right and a left to you and that you move in space will affect cascades of things that will adversely impact your life.
Cardinal movements should be developed by the time you sit which is around six months old. If you spot things that concern you in the way a baby is moving or developing, you should be trying to deal with it straight away.
Is crawling a cardinal move?
Crawling is a cardinal move. But it’s an integrated movement as well. It’s one of the important ones because it brings together left and right, top and bottom in a coordinated fashion. You need this to be able to do to keep your balance and to be able to see far and near. It impacts vision, for your eyes to be able to come closer and further apart, which affects your ability to read across a page. It affects your ability to keep your arm steady while you’re copying and moving your head. It affects how you ride a bicycle and several components of swimming. This one is a big one.