Is there any explanation for the lack of pikes? It seems stupid considering Warhamster is all fake renaissance and pikes defined the era historically. I mean, zweihanders and halberds were used to counter the pikes... although I suppose in WH they are used against tough monsters. Still, I imagine pikes would be excellent in, say, stopping ork charges.
I think it's just a matter of no major faction being based on a Latin and southern European nation, and those are the ones who are best known for pikes. The Spanish and Swiss in particular. I know the Germans used them heavily as well, but they still tend to get overshadowed in the retrospective milieu by the anti-pike weapons – the ones that the Empire uses heavily.
Not really. I would guess it would partly be due to difficulty when it comes to the tabletop. How pikes would allocate hits if charged or charging, turning and reforming, ranks and number of hits and so on.
There is precedent for some of those mechanics though, spears have been able to hit using the first two, or three for High Elves, ranks when charged and elves have the "Always strike first" rule. I don't think there is really an answer for the lack of pikes.
Mechanics aren't the reason. Although it's a problem, it's a solvable problem (as the things you cite illustrate). If GW really wanted to add pikes, they would have.
Reading the wikis, I notice a lot of Tilian troops / mercenaries use pikes.
I don't suppose anyone can find anything about how they work mechanically?
Well, I'm pretty sure an armored knight and an armored warhorse are a combination more massive than an average orc boy (big ones not counting). Despite this, heavy cavalry was not used to charge pikes unless there were situational advantages. The bigger the attacker is and the harder they charge the pikes, the worse they'll impale themselves. Plus if the first rank of pikes breaks, there are many more ranks behind them.
What makes them good pike-breakers isn't the forward motion, it's the lateral motion. Halberds and zweihanders achieve this by being long, but orks can achieve this by being real strong. A horse is also strong, but doesn't add this strength to the strikes of the wielder and can't attack with transverse blows; the kind needed to break pikes.