Why would someone argue that the electoral college system should remain the same

The Electoral College should remain the same for various reasons. First, if it were not for the Electoral College, large states, such as California, would largely control the nation. The Electoral College is designed to maximize states' rights. For example, if the U.S. were a direct democracy, Hillary Clinton would have been elected as our president, even though approximately 90% states supported Trump. With the Electoral College, each state has 2-3 Electors for each Political Party. If the majority of the state votes for Hillary, the democratic electors for that specific state get the vote. If the majority of the state votes for Trump, the Republican electors get the vote. The system is designed to maximize sates' rights and avoid impulsive, mass decisions.

The theory is land mass basically what they said.

Assemblies do not have written codes of laws. laws are matters for magistrates and courts, not assemblies. codes of law are things such as civil law, criminal law, and constitutional law. what assemblies have are procedures regarding debating, voting and other business they might carry out.  also note that rome had three assemblies: the assembly of the soldiers, the assembly of the tribes, and the plebeian councils.