Achiephies are bad for games.

Developers and publishers love them because:

1) They're totally disconnected from games so they're simple to make.

2) They know obsessive people will chase them no matter how trivial they are, which pads out playtimes and encourages these people to hang onto their games slightly longer. Instead of making new levels or challenges, just add a bunch of pointless collectables or inane missions ("jump 100x in one spot!") and presto, another few hours tacked onto the game.

3) They can track how many people do what in games, so they clearly know how effective they are (see point two).

4) They're advertising for games as they broadcast to your "friends" what you've been playing.

Etc. I have to go to bed soon.

Achiephies are also bad for people.

1) Most of them are really dumb. How is finishing the tutorial an "achievement?" It reinforces the idea that many people will only do things if they get a reward for it. "You put your shoes on in the morning? You deserve a trophy!"

2) Your primary goal when playing a game should be playing the actual game, not the metagame around it.

3) Remember games before achiephies? Did people not replay them? Of course they did. They could even use something called their imaginations to come up with their own secondary goals, like speed runs or beating levels without getting powerups or whatever. So now, people will only do things if they can brag about it to their hundreds of friends online? (See point one.)

4) They're distracting. Or if you find you can successfully ignore them, then they're training you to ignore information coming at you. Either way, bad.

Etc. I still have to go to bed soon.

Yes, achiephies are "optional" in the sense that you don't have to do them in order to beat the game but they reinforce bad social habits and lazy game design. I also know of no system where you can make an account (which can have other benefits such as matchmaking and cloud save backups) but TURN OFF achiephies. If they're so optional, why is there no option to do so? Hmmmmmmmmm.