Bitcoin's consensus is different from the popular meaning of consensus. In Bitcoin, there is no fixed board of members or a jury which needs to form a consensus. All members of Bitcoin are in consensus as soon as they join the network. If someone disagrees, they can either leave the network or convince others to start a new network (a new coin).

Generally, large networks are more useful for each member and more secure due to risk sharing.

PS: This is an attempt to simplify Eric Voskuil's Crypto-economics one chapter at a time.