Forge stuff, what?

Played before the 3 player patch (kinda killed it for my friends and I) but I came back to check out. Why did they add this forge mechanic? Seems annoying ? Crafting items to be able to purchase in game? what ? have to grind stuff out? Do these things disappear after use ?
Sorry for sounding like a noob but as a returning player who hasn't followed devolvement these changes feel really bizarre and pointless, at least at first glance
//rant