Those people claiming bitcoin is scam, they are noobs on crypto currency trying to be on hyped train just wanted to fit in and make venture with but they don't really know what bitcoin is. They are just crybabies and weak hand holders wanted to make profit fast and easy but hey that's not how bitcoin works or any crypto currencies at all.
Bitcoin earnings and profits is not instant and have to work for it. Some people claim it is scam because they find sites that tells to earn with no work to do but have to put investment which sometimes is not true that makes them lose and untrust what they believe in first. They do not find better way of earning and stop though there are lot of people involve in it and continue earning.