Like most things today those phones are in a way a disguised scam, since there is so little difference between the models sold last year and the models sold today, the same happens with video games in which a game like FIFA has almost no changes from one version to the next and yet you are expected to pay the full price for the newest game, plus all the microtransactions needed to unlock the full game, and taking all of these factors into consideration it is not rare that people are changing their spending habits and they are keeping their phones for a longer period of time.
It's true. There is nothing inedit being launched nowadays. Everything is a copy paste from previous products. People want the profit, but don't want to put any effort and innovation in order to achieve that profit. I think people who still purchase items in a yearly basis are doing this for the sake of boasting themselves towards their social circle, because from the functional point of view, it doesn't make any sense.
The gaming, movies and music industries are another good examples of stagnant niches of the market, where profit is desired without giving anything constructive and thrilling in counterpart.