During the COH 2 Beta before the game launched. People complained about performance issues for the game and rather than fix the issues, Relic limited the population cap. They also did not have a heavy tank limit which stayed after launch so you often saw multiple IS-2s vs Tiger tanks in matches assuming you were able to deal with the immense lag at the time since they didn't have servers for multiplayer and it was P2P based.
100 pop cap is about perfect, it's more fun to manage a smaller army where every unit counts