The people who run that site are using a 3rd party survey/offer scheme for money. They even state that they don't guarantee that you will get a working code (translation: you won't get shit, but it's in the fine print so you can't sue us).
Excerpt from their Terms of Use:
After completion of all of the required steps, the participant might be given a code for Riot Points. Due to many factors, there can be no guarantee that the given code will be working, or has ever worked. If the codes are not working, we urge you to buy them directly from the store, located in the League of Legends game client.
This site is not intended for actual free League of Legends Riot Points codes, but a chance to receive one. It's your own responsibility to use codes. The chance to receive a free Riot Points code is offered as means of the website compensating the participant for his/her time, taken to complete the necessary steps. We claim no responsibility for the surveys people take or offers they choose in order to prove that they are real humans, operating the website, as we do not influence any decisions, meaning any costs from accepted offers are not under our jurisdiction, hence we cannot be held liable for such costs. We try to provide as many "no cost" surveys as possible; however, it is country-dependent.
Surveys/Offers are usually, but not limited to, free and are placed only in order to distinct a real human from a robot/bot (for example mobile-surveys are cost-dependent on your mobile service provider). It is under your own responsibility to choose one verification method which fits you. We take no responsibility if you decided on a paid-survey/verification.
It's a scam. They get money from gullible people who think they're getting free swag, because participation in those 3rd party surveys/offers means their advertisers pay them. It's a risk for participants because a lot of offers associated with those services are set up to phish identifying information, and some actively attempt to infect computers with malware and/or steal financial data.