Many people prefer not to spend money, especially on games unless it's a very good game. Free-to-play games promote more players, and allow more players to enjoy the game. There are many popular games that are free to play, such as League of Legends. The game is extremely successful and fun! It allows you to play with other people who can't afford to pay for games.
Although I do agree with the point that free-to-play games do pull people into buying more items and stuff like that, I think it's a good concept. For example, with Team Fortress 2, (the game in the picture) you don't miss much from not purchasing things in the store. Other games that claim they are free-to-play, where you need to pay for everything, are bad. It's a great idea, I just want to see it being executed better more often.
Allowing people to try out games makes them want to play more game which is not only good for the companies but also for the people who play the games. This will boost the economy and the amount of people who are happy (from games). Later on people will eventually PAY for other games which is good for the game developers.
Free to play games are a good idea, but only in moderation. Free to play is good if everything is balanced out and nothing is unfair, but it is a bad idea if everything is ridiculously overpowered and only items can be bought with real world money. It all depends on the company.
Free to play is a good concept idea, but rarely is it applied well. More often than not, game companies market the game as "free", but then sucker the players into paying real money through micro-transactions and buying in-game items so that they can keep up with others that have paid money. Companies that produce free to play games typically also do not have as much of an incentive to update the games, resulting in cheaper, but lower quality games.