No, trust me, it was not hard to play CS if you really wanted to. If you're a player that had the ability to go to EVO and play BB, you probably were already playing CS.
This difference between now and then is, then, they were already playing the sequel in depth and were practicing up on it. They had already moved on from CT and had preferred CS. Very few would want to go back, practice a game they didn't like for the express purpose of playing it once, and then forgetting it exists again. For all intensive purposes, the sequel was already out. It'd be like everyone playing Ultimate MvC3 for a month and then EVO says "Oh by the way guys, you have to play Vanilla for EVO". Yeah, no.
Unlike now where, outside of demo opportunities, very few from what I know have their hands on Extend. It's not like everyone's playing it and they have to go back to CS2, CS2 is what they have now. It's what the majority is playing now. Thus that's the game you play until the new shit comes out unless you straight don't like CS2. You shouldn't sit on your ass saying "Well...I like CS2...but Extend is coming out in two months which makes this thing useless, time to put it away and not bother playing it with anyone until then". Like, I don't get that.
Yet again though, I'm not part of the community, so if Zabel or someone else wants to shed light as to why BB players do this, and why it's completely justified for you guys, then please by all means, share.