I think there are more people joining 6s than leaving. There are various reasons people could stop playing 6s, like work schedule, school, bored of TF2, the reason you mentioned (if this were the case), and others. I don't think 6s is dying, and I'm not implying you said that, but I think 6s is actually increasing, just slower than people would expect/want.

As for HL, I feel that's more "popular" because there are a shit ton of TF2 players who just think it's better to play a game with all of the classes available and with more weapons. That and Valve seems to mention HL more than 6s. It's easier to get into HL than 6s, and it's easier to get people interested in HL than 6s.

In a way, I feel like I can almost guarantee that if the 6s community were as into growing the community so much back when it started as we are today, then it would be a whole lot bigger.

6v6 will always be the pinnacle of competition because prizes drive the top of the scene

prize money is too diluted among 9 players and travel expenses are far too prohibitive for any LANs to happen

Highlander is more popular because it doesn't exclude people who don't main scout, soldier, demo, or medic. If the class you enjoy most is spy it doesn't make sense to pick up 6s where your team will rip you apart in mumble for trying to spy to mid.

Highlander is also less of a time commitment than 6s. You have 9 people to schedule around so normally you dedicated 1-2 days of the week to scrims and 1 to the match. In ESEA you find scrims every day Monday-Thursday (some teams scrim weekends as well). You have to pay for the league itself, the atmosphere is more competitive, and you have to spend more and more time on the game if you actually want to get a decent standing.

TL;DR: HL is a lot more accessible for people out of pubs than 6s.

top teams, veterans to this game play for 6v6, ESEA supports it...playoffs on lan etc all those good perks are the driving force behind the comp scene for this game.

highlander is just for fun, and will never be as competitive as standard league play there is no sugar coating it

thats like asking if gun game mod will ever be more popular than standard 5v5 play in CS

highlander is definitely a "for fun" league

highlander is glorified pubbing, and due to the structure of this game, pubbing does not make a great competitive game.

the thing about tf2 compared to other competitive games is

dota pubbing ~ dota comp
starcraft pubbing ~ starcraft comp
quake pubbing ~ quake comp

All the games above have very similarly structured competitive and pub environments. You don't really fuck around in a game of dota, a quake duel, or a starcraft game like the average pyro in your 32 man server does.

tf2 pubbing ~ highlander if anything, which is why pubbers gravitate towards it if at all.

Also, I can only imagine the ESEA Highlander lan. "Our engie doesn't get here till 8:00".

to be completely fair highlander is a hell of a lot of fun (and you get a pretty cool medal misc) but it's hard to take it seriously as a competitive format when you have heavy mains

TLR hit the nail on the head. It's a much smoother transition for highlander, especially since all of the major pub (Engee, heavy, sniper, spy, demoman) classes are played whereas 6v6 demands scouts and soldiers.

Furthermore, I would say one of the major checks on the growth of 6v6, just as far as the raw number of teams, is the time commitment that's required. Most 6v6 teams scrim 3-5 (or more) nights a week, whereas many highlander teams only play their Monday matches or scrim only once. It's just a lot easier to ask people for 1-2 nights a week, the same time every week, than 3+ with constantly changing match dates.

There's also a lot of space in the highlander scene. Any random pub player could get 8 buddies and make a team, and play teams of equivalent skill level, whereas if the same were done for 6v6 they would have a very difficult time finding productive scrims.

I think the problem is that 6's has no ugc iron equivalent. There are no leagues or divisions where the average player skill level is equal to the average pubber. Even low steel players are significantly better than the average pubber.

Average players that try and get into 6's are simply not good enough to compete with anyone.

another reason why highlander is growing faster than 6s is because it is taken so much less seriously. Simply playing highlander for fun is actually quite possible, but playing 6s without taking it moderately seriously will eventually lead to a bad time, as your team gets crushed by people who take the game way more seriously than you do. I think highlander growing is a great thing for all kinds of competitive tf2, and will help both scenes grow. The people who want to take the competition up a notch will move to 6s soon enough, while people who commit much less to the competitive side of tf2 will continue to grab interest from the masses.