Ohhh, katieemily, katieemily, katieemily - do you not realise that the baby food manufacturers are more interested in selling you baby food than in your baby's welfare? Profit is all that matters to them.
If they start marketing baby food from 6 months instead of 4 months, that is two whole months of income from gullible parents that they will lose.
But if you would prefer to take the advice of people who have an ulterior motive for their advice than the advice of scientists who have your baby's best interests at heart, then there will be nothing we can say to convince you.
You might be interested to know that cigarette companies used to market their product as being good for your health - indeed, cigarette companies had adverts with doctors endorsing their brand. And of course, initially there was no scientific evidence to counter these claims.
But now there is a mountain of research proving the link between smoking and cancer, smoking and cardiovascular disease, and smoking and other conditions - so the medical advice has changed.
You need to learn to look critically at what you are being told, and work out whether the person giving it has an ulterior motive (selling you baby food, so they make more profit) or whether the advice is impartial. You haven't learned that yet.