I was going to write my interpretation but @SDC seems to have covered most of it, so I’ll add:
The entire dhamma must fall under the 4 noble truths, especially the first two.
The first noble truth clearly states what the problem is, and that is clinging to the five aggregates, which means the body and mind.
The body is a huge source of suffering, and we think we’re in control of it when in reality the circumstances are only temporarily favourable and we confuse this for control, but when the circumstances swing the other way and you can’t sleep for a month due to anguishing pain then you’ll quickly realize that “the self in control” has become “the self that is a slave to this body”.
Any view regarding a self is clinging to the aggregates.
So form means the body, and nama means the mind.
So to answer both OP and @knotty36 - The purpose in seeing the body as the 4 elements is to depersonalize and forfeit ownership of the body. The elements in the body do their own thing, when the elements do a random combination of rubbing eachother, the circumstances are favourable and the body is invisible. When they do another random combination of rubbing eachother, the circumstances are unfavourable and you have hellish anguishing pain for a month. Eitherway, the self has no say over the 4 elements, as the self is dependent on having a body which is dependent on having the 4 elements, not the other way around. If the 4 elements were dependent on a self, then one could merely wish for pain, disease and old age to instantly disappear.
So the function of the 4 elements is to see the dependency (Idappaccayatā) of things, and adopt the proper attitude. The proper attitude towards something that is not in your possession or control is to have nothing to do with it, to let it go and leave it alone.
As per Maha rahula sutta
Develop the meditation in tune with water. For when you are developing the meditation in tune with water, agreeable & disagreeable sensory impressions that have arisen will not stay in charge of your mind. Just as when people wash what is clean or unclean in water—feces, urine, saliva, pus, or blood—the water is not horrified, humiliated, or disgusted by it; in the same way, when you are developing the meditation in tune with water, agreeable & disagreeable sensory impressions that have arisen will not stay in charge of your mind.
If your view, attitude and habits aligned with things as they really are then you would not try to have more pleasure when it is present or get rid of pain when it is present, instead you would be equanimous just like you are equanimous with observing things happening to other things in nature which have nothing to do with you. Likewise the elements, and therefore the body, have nothing to do with you.