There's a number of possibilities. Orally consumed drugs are more subject to first pass metabolism. For example, cannabis when consumed orally is metabolized into a cannabinoid about 20% stronger by weight than delta 9 THC. The opposite is true with morphine, when orally consumed about half of it is converted by the liver into a metabolite which has no activity. So even after accounting for absorption efficiency, oral morphine is only half as strong as parenteral morphine. Then there's the speed of onset and speed of elimination which I believe can cause profound differences in the effect of psychedelics, especially ones with what I (perhaps naively) consider to be a pharmacologically complex compound like MDMA. Like I stated before, insufflated MDA has never been fun to me, although insufflated mdma can be.