There are many reasons to be sincere, but in my opinion, some people may decide to conceal their information in order to get an advantage over rivals. The other explanation is that they might not feel enough secure in their views or information, which would cause them to keep it to themselves. In the case of Bitcoin and cryptocurrencies, some individuals may opt to keep their information to themselves in order to safeguard their assets safe or the manner they obtain their assets may be utilized longer while still few people understood it.
Its all best known to each individual why they feel they shouldn’t share their knowledge with others.