Riot has been under fire for the exorbitant cost of champions. At the rate of one loss and one win per day, it would take you over four and a half years to purchase every champion.
If that seems like a long wait, consider what exactly that means. If somebody is only playing only two games per day (let us assume those two games are on the same champion), they would need to play for 121 days to even have played every champion.
This problem is easily solved by the free champion rotation. Every week, 10 champions, stratified by role and cost, are free for all players to play. In the last 7 months, every champion has been free but for six:
Gnar, of course, has just come out, and so has not yet been free. As usual, he will be available for free 2 weeks after his release. Poppy, Sion, and Yorick are all champions considered to have problematic kits by Riot, and are all currently being reworked by the design team. As such, they have been kept out of the free rotation, as they could be confusing or frustrating to new players to encounter.
This leaves two champions who has not been free in 2014: Alistar and Tristana. You can get those champions on your account for free simply by liking League of Legends on Youtube and Facebook respectively.
So if your goal is merely to sample every champion, it would not take the four and a half years many players have complained about, but rather 7 months or less. On the other hand, if the player is intent on consistently playing all champions, well, they will be playing more games, earning more IP, and unlocking the champions much more quickly. Either way, it’s a win-win situation. The hardcore players will unlock more content so they can be more hardcore, while the casual players still get a constantly evolving game through the free week rotation of champions.
To make my point abundantly clear: if you’re actually playing enough to be able to take advantage of owning more champions than a few core ones and the free week rotation, then you’ll be able to afford the champions much more quickly. On the other hand, if you’re not playing the game more than once or twice a day, you wouldn’t even be able to use that champion pool, so it hardly seems a big deal that you won’t be able to afford it that quickly.