Your "confidence" is wrong. Consider a graph which can have nodes added, and edges added or removed. Say you want to keep track of the part of the graph that i

Your "confidence" is wrong. Consider a graph which can have nodes added, and edges added or removed. Say you want to keep track of the part of the graph that is connected to a node. You can't know ahead of time which references can be weak. So all must be strong and you will leak memory when a circular part of the graph becomes disconnected. In general, garbage collection is a difficult problem that solves a lot. You can't trivially do without it. It's not just a tool of laziness.