EB Roman history differs from real Roman history in a number of ways.

In EB, there is no Roman civil war.

But in EB, Rome eventually has to fight a huge war against a mighty Ptolemaic Empire in order to gain Egypt. (Or a mighty Seleucid Empire, depending on how things go.)

This did not happen historically, since the Ptolemies basically destroyed themselves as a major power through internal struggles before Rome ever got there - so Egypt was an easy conquest for Rome. The Seleucids also destroyed themselves in dynastic power struggles.

So it balances out. We could say that the EB Rome can't afford a civil war because she has to fight stronger external enemies than the real Rome had to.