A person can agree to one part without accepting the whole responsibility around it.

Saying yes to a task often carries an unspoken extension: you are now the one who handles this area, chases the related problems, and gets asked about it forever. That expansion is never negotiated, which is why people become cautious about small yeses. The caution is not unwillingness but a reasonable defence against scope with no edges.

When you agree to something, say what you are agreeing to and what you are not. If you are the one asking, describe the boundary yourself, and resist adding the neighbouring problem later just because they were helpful once.