Slow work day, so I have time for this.
OP (short): Achievements are basically a visual representation of your in-game accomplishments; A ranking system Leaderboard for FFXI players.
Everyone else (long): I always feel like its a "let people have their fun" moment. It shouldn't matter if some people value achievements no more than it should matter if someone
chooses to spend 500 million in-game currency on one item, or if someone
chooses to spend their vacation catching rare pokemon rather than sight-seeing. It's their choice, and it doesn't affect you at all. So at the end of the day "it doesn't matter", or at least shouldn't what another person values.
Personally, you won't catch me giving a crap about an "achievement", because I'm not wired like that with the Leaderboard mentality to "be the best" amongst 'peers' of other gamers. You can check my online profile; I have no picture and have never registered my account for achievements (don't even know how to). I don't even use the third party software many others use. I just don't care enough to min-max every possible instance, and I have no interest in an online competition of others. It just does not matter to me at all to have a visual recognition of my gaming-work, whether from other players or myself. However, I do use scoreboard to test how I stack up against other players.
On the other hand, some people take great pride in their hard work, since achievements and character building is basically like a Gaming Career, to an extent. It almost validates them that they worked hard at something, and others can appreciate (or hate) on their accomplishments. That can be respected, or ignored. I couldn't tell you who the top ranked player of any server ever was, because I don't check people or leaderboards, but it is cool to have players at that level. You can't deny that it is an accomplishment to be one of the best among your peers
That doesn't mean those who do seek that kind of approval or recognition are "losers". There are some people who seek
that very same recognition at home, on the job, on the internet with people who could not give a ***about them (see: instagram models, twitch chicks), in the gym, and in society in general. Many people I know (most of them being my close friends) have that same mentality about competing with their peers in "Life" - they will look to date prettier girls and drive nicer cars and make more money; Not for their own happiness, but completely for others. To an extent, it's sad to me, but it is human nature to want recognition from others. Literally every person looks for some kind of recognition in some area of life, so it shouldn't be frowned upon for "Gamers". If it's not your cup of tea, keep it moving.
Just let people have their fun is how I feel about it. If the guy in the gym is jacked and ripped to shreds, why do you feel so insecure about it that you have to discredit his accomplishments? The whole "he has no life" argument reeks of insecurity. Yes, some people don't have a life, but let them dig their own grave I always say. You gotta just let people do what they want and do what makes them happy.
The only time I really am bothered by people with the whole "achievements" argument is when people start creating artificial standards based on
their accomplishments and start judging others by it. As if you're not anywhere near their level just because they said so.
i.e. "I CREATED THIS LUA FROM SCRATCH, YOU FKN PLEBS BETTER NOT ASK ME FOR MINE, SIT THERE FOR HOURS AND WRITE YOUR OWN. Oh you can't? LOLOL SCRUB"