I am of two mindsets on it:
1. It's common in these forums because they're dev forums. So, acceptable.
2. Outside the dev forums, I'm not a fan of it.
1. I don't mind it done here, on these forums because it serves several purposes. The main purpose is just as a means of "belonging" to the community. Posting your progress typically comes with posts that say "great job!" or "hooray!", as honest or as fake as those replies can be. Using that advertising as a means of "connecting" with other devs in a forum about dev work isn't wrong or bad. Likewise, such advertising usually comes with the promise of "a demo" or some other stuff to play so the dev can get actual feedback. So, it's utilitarian in nature. I find all of this to be pretty acceptable and reasonable.
2. Games outside a dev space being advertised 1 or more years out... I always have to wonder "what's the point?". You may have an amazing idea for a game today, but with a release date of "who the heck knows when?", I'm probably going to forget your game exists and not follow it until, you know "it's almost ready to launch". Now, if you start advertising like 3 months from launch... awesome, I can probably maintain my interest for 3 months. But, more than that? Eh.... Unless your game is "The Second Coming of Christ" or something equally as impressive... I'm just going to forget it exists since there's a deluge of good games already releasing between now and your release date.
I think what I, and many other people are prone to is just, "Oh, you're making a game? Nice. I'll come back when it's almost finished". Which usually translates to "If I remember your game exists 6 months from now".
Here's the way I tend to think of such practices:
Let's say you own a retail store. You have plans, six months from now, to sell Blarg Brand Fried Chicken. Awesome. It's Fried Chicken! Blarg is also known for having really amazing Fried Chicken! I can't wait to come and shop in your store for that chicken!
But, it's six months. I mean... I kind of want the Fried Chicken now. So, you know, I'll go to KFC or something today. Fill my desire for Fried Chicken there. Maybe go to Chick Fil-A. Or, you know, whatever. Spend 6 months filling my desire for the Fried Chicken experience. So, I forget you've got these advertisements up all over your store about Blarg's chicken. Or, you know, I tune them out. Because, they're the same thing today as they were 3 months ago. Or, I stop caring about Blarg's chicken because I already had my desire for Fried Chicken fulfilled by someone else. Sometime else. Now, when you launch Blarg's Fried Chicken at your store... I might pick up now and again. But, unless it's like "you have a foodgasm upon eating" quality, I'm not going to have hype for it.
Video games are like this. It's a saturated market for a limited use product.
Think of everything you can advertise about your game and then go, "How many other games in the history of video games have this same feature, and how many of them are doing it better than I do it?". Then ask, "How many more are going to release before my game and overshadow it?".
The movie industry has this problem. Some movies... REALLY GOOD MOVIES get "passed over" by audiences because something else was showing in the same timeframe. It's why they have "dump schedules" for plenty of movies. Places where they dump specific films in the year that they don't think are projected to do very well.
Video games have this same issue. If you release an inferior quality game too close to one that does the same stuff yours does... yours will do poorly.
This is why I rarely understand why game studios spend so much time and money trying to "hype" a game up like months or years in advance. If your game does poorly, then all that money you spent on "hype" and all that time spent on generating interest was a waste of time and money, which means you're garbage at marketing and managing time/money investment.
But, hey, you could just take me for an example:
Look at my signature line about my game progress. I don't think that part has changed for like... 2 or more years. Sure, the data has changed, but I never updated the signature. Do I got anyone asking me about my game and the release date or anything based on that constant advertisement? Nope.
When do I get questions about my game?
Typically when I make a post that makes it sound like that my game is actually already completed or in a very playable state. Then, I get the occasional PM asking where to find it. Or, sometimes, the random reply in the forums asking about my game and how it plays and more details on the examples (as if those things were 100% playable and not just used examples of things my game does).
Interest is typically most generated when you go, "I have a game that's basically playable right now". When you state, "I'm working on a game that will release in 6 months", you aren't generating that much hype unless it's "No other game on the planet does what mine does".