Why is silk haram for men?

So the Prophet mentioned this in Sahih Bukhari and Sahih Muslim and the reason for the prohibition is that silk will be the clothing for men in Jannah. So that's why it's not for now. It's for Jannah. Also important to note that it's only pure silk from the silkworm. If it's synthetic silk which most items are nowadays because pure silk is very expensive then synthetic silk is fine. It's pure silk from the silkworm. That is what the prohibition refers to.