Memeplexes are collections of memes/concepts/ideas which have coalesced together to form a coherent body. Religions, world views, and belief systems are memeplexes. They may modify themselves and evolve over time, but they maintain their core message or character.
Genes are to organisms as memes are to memeplexes. Like organisms memeplexes want to survive. And, as with organisms, this drive for survival arises due to selective pressure. Organisms and genetic lines which do not develop self-preservation tactics simply do not persist. So whatever organisms are left after the simulation has been run for a while have strong drive for survival. The competitive landscape itself ensures the development of the will for survival.
It’s the same for memeplexes. They exist in a competitive landscape as they must compete for the mental bandwidth of their hosts. So they tend to develop self-preservation tactics. Religions always try to win converts. Political ideologies always try to gain followers. Even broader world views and more general philosophical outlooks fight for their territory.