Picture logging on nearly every night with one country outnumbering the other two combined...by as much as 100 or more people on the weekends.
Indeed.
Imagine flying for the country that had the huge numbers (Rooks iirc) and trying to score a kill while 20 of your team mates try to beat you to it. Imagine what it was like to fly for either the Bishops or Knights and getting steam rolled by the Rook juggernaught every night.
That is why we now have ENY. ENY hasn't forced sides to be equal every night but it has prevented one team from becoming so populas that it outnumbers both of the other 2 combined.
HiTech has said (paraphrasing here) that they didn't want to force us to do things, but instead, to give us options and incentives. ENY accomplishes that most excellently.
Your options are: 1) Change countries to help balance things out. 2) Don't change countries and pay a penalty in a restricted plane set.
In regards to number 1, many are not inclined to switch sides for various reasons. The incentives to do so however are, reduced costs for perk planes, more perks earned per kill, an unrestricted plane set and the opportunity to meet folks on other teams.
In regards to number 2, you pay the penalty based on YOUR choice to not switch sides. The penalty also includes fewer perks earned per kill in addition to the restricted plane set. You also don't get to build relationships with folks from the other teams. There are many people worth knowing on all 3 teams.