To the Hebrew audience, leaving Christianity was simply a matter of convenience and nothing more. What they were used to was better than what they currently had or so they thought.
In Hebrews 6 the Hebrew writer pauses his discussion of the high priesthood of Jesus in order to correct some very wrong thinking. Leaving Christianity for Judaism was not just a simple change, it was an act of treason against God. In fact, leaving Christianity for Judaism was akin to crucifying Jesus for a second time (Heb. 6:4-6).
In urging them not to leave, the Hebrew reminds them of some “better” things they have, specifically regarding their salvation (6:9). What they have with Jesus is worth holding on to and the same is true with us.
Everybody today, whether they refer to it in this way or not, is looking for salvation. Some turn to music, relationships with others, hobbies, and even things like drugs, alcohol, or pornography to find freedom from their every day. Ultimately those endeavors prove themselves to be a waste of time never being able to solve our problems of loneliness, pain, and above all, sin.
This is not so with Jesus. With Jesus we are not left wanting or disappointed. In Him we find a message of hope and grace. In Him we find One who can identify with our weaknesses (Heb. 4:14-16). Why look for salvation anywhere or in anyone else? Jesus offers the best salvation possible.