It's mostly because there isn't a lot of good spears out there and those that do takes an enormous amounts of strength and dex which leaves less room for vitality. You're also giving up a shield that is, for most people, their source of resistance. I played one a while ago using WW, it didn't turn out as well as I had hoped. I ended up wearing the Viperfork for the longest time and gave up on it before I got to 81 for the Arioc's Needle. My barbarian couldn't kill anything, plus the WW glitch on it (not sure if it still exists) was annoying and got me killed several times.
Well,ww hit rate depends on your on-weapon ias.So thats why unlike classic you dont see many lance barbs,since the actual "lance" exeptional spear or elite warpike cant hit the last ww bp with any r/w.The spire of honour & steel pillar are too slow as well.
If you are olschool & have a liking to lances then a 'robopike' is the weapon for you,it does hit lwbp,you'll be able to make on on nl with an eth warpike with 4x 40/15s(dupealert)/zod & shael.But the dmg is sub par when compared to botd gpa or botd gs which have more benefits in mods like leech/stats etc.
So if you are looking for spears in general botd ghost spear is the weapon for you,on budget, then an eth upped hone sundan yari with triple shaled is damn effective as well.