The problem with crafting. Anything you make would have to be of lesser quality than an item found in engrams or even strike/raid drops, simply crafting the best gear would just cause ppl to farm mats. Second thing is that those crafted items would take more resources aka disc space. So which would mean less unique armor designs and more re-skins of older armor within the crafting profession. But to put the nail in the coffin, is that with a small and easy soft lvl cap to reach, having a profession like crafting would be pointless. Once lvl 20 we already find light gear up to lvl 24/25 and start to find legendary gear. People would be wearing marks, bonds, cloaks from reputation rather than craft them and everyone would just push crafting to the back burner. Even if they had say legendary blueprints for gear it would still have to be put geared by raid, rep gear. And if they put trading in the game it would mean an entire revision of the loot system and crafting to trade would be pointless because everyone would could do it.

I have to answer maybe and say that there technically is crafting in the way that you upgrade weapons

I don't see why not but at the same time I don't see a reason for it. Right now id rather bungie focus in expanding the game as it is before adding something like crafting.