The Veritech/Variable Fighter, by my understanding fights in three general environments: Space, Atmosphere and Surface. For the most part they can move freely between these environments (excepting the VF-1 and other early models that couldn't reach orbit unassisted). Ton for ton and dollar for dollar, you'd expect it to be more efficient to build specialised units for each (and to some extent this probably happens, thus the humble Destroid for surface battle).
However, there are generally quite substantial limits to how large the deployed forces could be early on, pre-Space War One there were a limited number of major combatants in space so hanger-space was limited. And from the start of the war on the SDF-1 and post-Rain of Death military had significant manpower limits so having one-man units that could handle any of these situations fit the needs much better than a wider range of capability. This also established the VF pilots as the elite group who could go anywhere and do anything. It'd be interesting to see how this might have developed if Space War One had involved more conventional forces from Earth rather than such units being largely sidelined until they were bombarded into oblivion.
In terms of capability, the VFs seem to handle the roles very well. They can carry large missile loads for high speed, long range engagements in space and atmosphere; they can also handle space boarding actions and urban combat, which also come up quite a lot. And they do so just as well as dedicated fighters/ground units, so there's no real demand to substantially increase numbers of units limited to a single environment (although no doubt some exist). This is quite unlike Battletech were Land-Air-Mechs are significantly limited compared to more specialised units.
D for Drakensis
You're only young once, but immaturity is forever.
However, there are generally quite substantial limits to how large the deployed forces could be early on, pre-Space War One there were a limited number of major combatants in space so hanger-space was limited. And from the start of the war on the SDF-1 and post-Rain of Death military had significant manpower limits so having one-man units that could handle any of these situations fit the needs much better than a wider range of capability. This also established the VF pilots as the elite group who could go anywhere and do anything. It'd be interesting to see how this might have developed if Space War One had involved more conventional forces from Earth rather than such units being largely sidelined until they were bombarded into oblivion.
In terms of capability, the VFs seem to handle the roles very well. They can carry large missile loads for high speed, long range engagements in space and atmosphere; they can also handle space boarding actions and urban combat, which also come up quite a lot. And they do so just as well as dedicated fighters/ground units, so there's no real demand to substantially increase numbers of units limited to a single environment (although no doubt some exist). This is quite unlike Battletech were Land-Air-Mechs are significantly limited compared to more specialised units.
D for Drakensis
You're only young once, but immaturity is forever.