Why use heavy infantry when I got elite pikemen?

[Slim_Ghost]

I found out that whenever I use any faction that has elite pikemen - Makedonia, Ptolemaioi, Epiros, Kardasthim, Seleukeia and Pontos, I find no use of it's elite heavy infantry it offers. These elite pikemen can easily double as elite heavy infantry when I disable the pike formation. Their melee ability is just as great as the hypaspists, or Galatian heavy infantry, or Sacred Band hoplites, or Galatian wild men, or the Ptolemaic Royal Guards, Armored Hellenic Spearmen, whatever. Even if they do have weaker melee, the elite pikemen more than compensates for it with their vastly superior numbers (in huge setting they number a whooping 240 men per unit!).

And besides, hypaspists are insanely expensive. Doesn't seem like a cost-effective unit for me. I just recruit them for the sake of roleplaying (I.e royal guards garrisoning the capital or surrounding the King in each battle), or if I am too lazy micromanaging pikemen.

Is there a tactical advantage of using them that I may have not noticed? Can any experienced EB player shed some light in this?