Anyways, since I know this will come up: Here is Bottiger's reasoning for removing "unpopular" maps, copied and pasted from his general post.
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Why do we remove maps if it is unpopular?
You can argue that people wouldn't vote for a map they don't like and if they don't vote they don't care.
However, the reality is that when an unpopular map gets voted in, half the server leaves. Even people who don't vote will quit because they were too lazy to vote or they leave because everyone else left. That's why we need to be proactive in removing unpopular maps.
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Dissection time.
Through my experience on the surf server, I know for a fact that a lot of people leave when rainbow is voted, a VERY popular map. I know that people leave when 10x is voted, air arena, etc.
People leave when prelude is voted, when halofuse is voted, when twilight is voted, when utopia is voted, etc, etc.
A server will always lose a chunk of players upon ANY map change, no matter what map got voted, for a variety of reasons (occurs an all servers on all valve games running any gamemode).
Map changes make good stopping points to disconnect and do something else.
Of course, you have the people who leave because they don't like the new map, which is fine, because no map will ever have a 100% approval rating with a player base (no matter how hard you try to make a rotation with only "popular" maps).
However, these players who leave are quickly replaced by new players, as the player drop from a map change to even the most hated map (10x, or revolution when it was still there) will never result in a full 32/32 server dropping to zero players because of a map, like you seem to imply.
Sure, "half the server" (exaggeration, the effect of a map change is not that severe) leaves, some because they simply want to stop playing, which has nothing to do with the map, and some who quit because of the map.
What happens next?
Those players are replaced by new ones and the server goes back to full (or mostly full, depends on the time of day since the server has peak and off peak hours).
I don't understand why Bottiger is so determined to hold on to that small portion of disconnects who leave because of the map that got voted is one that they personally don't like.
By constructing a small map rotation of these specific maps that appeal to the most players possible, you sacrifice variety and the ability for players to progress through the surf difficulty scale in order to have a chance at player retention.
But all people have their specific maps they like and dislike, people will leave as a result of (literally any surf map here) being voted. So what does the limited rotation accomplish, since ALL people will never be happy with any map?
Is the goal to retain as many people as possible? Because even if 5 extra people leave as an unpopular map is picked (versus "popular" map), they will just get replaced in 10 minutes anyways, and server is back to full.
The main reasons I see player counts drop is time, as players are lost during off-peak hours due to being late night or very early morning when very few people are even playing the game (Gametracker shows a regular pattern of player activity drops and increases over longer periods of time, with no sudden decline that is not present the day before).
Oh, and one more thing.
I fail to see how the frequency of a map being played, or playtime of a map, has anything to do with the amount of people leaving as a direct result of the chosen map. That seems to have much more to do with the quality of the map and play-style it promotes. (ex. utopia promotes camping by having very easy surf with sniper box as reward, but also promotes deathmatch type gameplay for those who want that, while rainbow promotes camping and farming to the elite who can finish that map, while the rest of the players (ones being camped) cuss at and vote kick/slay the few who finished the map and are using their earned rewards)
Since each map has a play-style that is optimal for that map, players who enjoy that play-style will like it, and players who dont, wont. There is no satisfying everyone. Stop sacrificing variety and progression (please actually read the bottom half of the rant post where I discuss this thank you) chasing this golden rotation of maps.