This has nothing to do with public ownership; it occurs with private ownership of the interior parcel as well. Are the outer parcel owners also unfairly encumbered by an access easement then?
This is a very real problem in some agricultural country! Not unusual for farms to purchase a field that is surrounded by other owners and then have a big dispute over easement to access. It's a particularly large problem in areas that were historically subdivided without road easements between lots (as is the typical modern practice), or that were originally subdivided for reasons like mineral exploitation that did not customarily use road easements.
Depends how they got that way. Will they pay for it? Perhaps they made an unwise investment and should have paid for more rights.
I have seen the case where someone buys a parcel from a larger property. Then turned around and demand easement access from the neighbor on the other side who was not party to the deal, because that neighbor has better roads and is easier to cross.