If you don't pin your dependencies, you will get breakage because your dependencies can have breaking changes from version bumps. If your dependencies don't fully pin, then you they will get breaking changes from what they rely on. That's why exact version numbers are almost always pinned for something distributed, because it's a frequent problem that you don't want the end user having to deal with.

Again, you don't see this problem often because you're lucky: you've installed at a time when the dependencies have already resolved all the breakage or, the more common case, the dependencies were pinned tight enough that those breaking changes were never an issue. In other words, everyone pinning their dependencies strict enough is already the solution to the problem. The tighter the restriction, the more guarantee of continued functionality.

I would suggest reading this comment chain again.