Local governance becomes more practical. There can be relationships involved. Mayors can have grown up in the area they are in charge of. They can have a sense of the community dynamics and how they are being affected by change. They can balance the pleasure of progress with a nostalgia for the what the character of the place has been. Local governance allows for tacit knowledge - the stuff we know but can't explain.
Local-Governance is not 'Self'-Governance. My issue with 'Self' is that it starts to create an exclusive community, set apart. The seeds that built Nation States, and self-determination may have had positive intent in terms of Imperial Governments forcing controls from a distance, but there have also been unintended consequences.