Though... I think only the presence of significant light to medium vehicles (or super inf) actually can favor that, because 1x HCAP and 1x HAV dishes out more 'kills infantry' and more 'kills heavy vehicles' than 2x HAC.
It is admittedly a specialized use case, which I think is fine as not every weapon type needs to be equally as commonly used. However, I definitely am someone who builds mechanized infantry formations with armored INF and LVH and I also like to use heavy armor (HVH) so in a multiple player race game I could see HAC being a useful choice.
IMO we need some way to get intelligence on what ground units the other races use, so that we actually have some motivation to design such specialist units. Currently without such information we have no good reason not to build generalist (or terrain-specialized only) units, and by the time we are engaging an enemy in combat to gain such information, well, ground forces take so long to build up that this is simply too late to count as actionable intel.