This might be an ignorant question, but I've always been a suburb dweller so I don't know. What's so special about the Esplanade? I've never understood why people are so passionate about it. What's so unique about it? And the whole Olmstead system, people revere these parks like they were crafted by the hand of God. Aren't they just a bunch of parks, just grass and trees? Honest question, no snark intended.
Well, they weren't "crafted by the hand of God"... however, they were crafted out of marshland by many, many men over the course of more than 100 years. Starting with Boston Common--the oldest public park in the United States--Bostonians and the planners of yesteryear purposefully constructed parks for the sake of those populating the city. The whole premise of the park, especially during the late 19th century, was to provide an escape for the people dwelling in congested cities... a retreat to nature, to breathe, to have a richer quality of life.
I cannot speak for others, but I'm passionate about the esplanade and other parks in this city because they not only highlight but also define what a wonderful city Boston is to live. Coming from South Florida where a park is only built because the developers were obligated to allot green space due to zoning code(s) (like most suburbs), Boston's parks are such a treat because the people really wanted them in the first place. Today, we still use and maintain these parks much like some upper-middle class suburbanites use their backyards, except we can bask in the shared experience of it unlike many in the suburbs that shut themselves off to their neighbors.
I frequent Boston's parks year-round: the esplanade, the commonwealth avenue mall, public garden, boston common, fens, greenways, SW Corridor, Arboretum. I feel healthier because of them (*AND actually my high blood pressure dropped immensely once I bought a bicycle and started riding throughout these parks regularly).
I'll leave the F.L. Olmstead 101 lesson to datadyne007 to explain the enthusiasm architects and planners share for the Emerald Necklace (among others). There is in fact a very exciting history to Boston's parks that merits the passion so many share for them.