Why isnt oxytocin available for those with lactation problem?

Business decision. Nasal oxytocin was made by novartis in 1980s=>very effective on well-selected lpatients in facilitating "milk let-down". It turns out now we know that part of the reason it worked is due to anti-anxiety effects. It was entirely safe & that was never a concern of the fda or the drug co. Breastfeeding enthusiasts inexplicably & misguidedly shunned it & the sales dropped. It's still sold in europe.
It is dangerous. Oxytocin is used to augment labor, and is also the hormone that is involved in let-down in a lactating woman. It does not really increase milk supply as much as it allows the milk to release. It is only used in labor under very careful monitoring because it can drop someone's blood pressure. Fenugreek, metaclopromide, and pumping are better options to increase supply.