My understanding is that the way pikes are used in the Medieval period, and how they were used by the Macedonians were very different strategically/tactically (I think this would be under tactics).
Macedonians used them as front-line troops, supported and surrounded by others, whilst my understanding is that later on Pikes were used as a way to create a fortress of spears to control the battlefield.
Now, as to why they fell out of fashion - they didn't, they became TOO fashionable, at the cost of the Mixed-Arms approach that were vital to their success, which mean that the Roman Legionairre, armed as a weird hybrid between swordsman, and dart thrower found themselves able to break through pike lines long enough to be inside their pikes and able to take advantage of their short range. Once that tactic worked, it could be re-used against the Diadochi who weren't as adaptive like Philip and Alexander were, and were too invested in pikemen to adjust their tactics to counter - this gives the Roman Legion a great reputation, and as such, impetus.
But that isn't to say we didn't see spearmen and pikes not make an appearance repeatedly before the Medieval period - https://en.wikipedia.org/wiki/Byzantine_battle_tactics#Skoutatoi is simply one example. Sure they didn't use the 4-6 metre long Sarissa, but 3 metres is still a damn long spear.
If the Diadochi or Greeks maintained their mixed arms, they'd probably have Legionairre style troops as flanking forces, or 'pike-breakers', but not entire armies of them - and as such use strategies closer to the late Byzantine Skoutatoi than Roman legions.
The main factor I think, in all honestly is fashion. I think you've got a combination of utility, combined with 'Military Fashion' - as in, it worked, and keeps working, so just keep the same idea going. After all, it is why the Romans used Manipular tactics, and why the Diadochi went big on pikes. Who says Militaries can't fall victim to their own fashions? Heck, what do you call the Somme other than "Walking walls of Line Infantry (essentially the ranged equivalent of a pike block) marching at each other always works - oh... Machine Guns".
So yeah, reputation in defeating a supposedly superior foe, and momentum.
Macedonians used them as front-line troops, supported and surrounded by others, whilst my understanding is that later on Pikes were used as a way to create a fortress of spears to control the battlefield.
Now, as to why they fell out of fashion - they didn't, they became TOO fashionable, at the cost of the Mixed-Arms approach that were vital to their success, which mean that the Roman Legionairre, armed as a weird hybrid between swordsman, and dart thrower found themselves able to break through pike lines long enough to be inside their pikes and able to take advantage of their short range. Once that tactic worked, it could be re-used against the Diadochi who weren't as adaptive like Philip and Alexander were, and were too invested in pikemen to adjust their tactics to counter - this gives the Roman Legion a great reputation, and as such, impetus.
But that isn't to say we didn't see spearmen and pikes not make an appearance repeatedly before the Medieval period - https://en.wikipedia.org/wiki/Byzantine_battle_tactics#Skoutatoi is simply one example. Sure they didn't use the 4-6 metre long Sarissa, but 3 metres is still a damn long spear.
If the Diadochi or Greeks maintained their mixed arms, they'd probably have Legionairre style troops as flanking forces, or 'pike-breakers', but not entire armies of them - and as such use strategies closer to the late Byzantine Skoutatoi than Roman legions.
The main factor I think, in all honestly is fashion. I think you've got a combination of utility, combined with 'Military Fashion' - as in, it worked, and keeps working, so just keep the same idea going. After all, it is why the Romans used Manipular tactics, and why the Diadochi went big on pikes. Who says Militaries can't fall victim to their own fashions? Heck, what do you call the Somme other than "Walking walls of Line Infantry (essentially the ranged equivalent of a pike block) marching at each other always works - oh... Machine Guns".
So yeah, reputation in defeating a supposedly superior foe, and momentum.