What are the reasons why a family of three refused to sign a Canadian tourist visa?

There are various reasons for a family of three to refuse a Canadian tourist visa, which are as follows: (1) Incomplete materials; The material is untrue; The purpose of going abroad is unclear. I know that there is an organization "Re-signing Network" that specializes in refusal and re-signing, but it is a bit expensive. It is said that there are some acquaintances with government background in the embassy. My colleague didn't sign it himself, nor did he find a small intermediary. Later, they found the "Re-reading Network" and successfully got the visa. However, this money is really not cheap.