McPherson's Testing the Current: Why is this a novel?

Not to "beat a dead horse," but I am continuing reading William McPherson's Testing the Current, out of loyalty and commitment to book group, but wonder how anyone could possibly make it through the long section on xmas morning (end of section 3), including some paragraphs that go on for several pages of dense text!, and to what end? Yes McPherson had a tremendous capacity to summon up remembrance of the details of his bourgeois Midwestern childhood, but how does this serve the interest of his novel - page upon page of the details of an xmas morning, the gifts received, the family visits, the phone calls to and from relatives and girlfriends, Tommy's visits to several neighbors, on and on about his gift - a small desk w/ lock and key, some fancy kind of Monopoly set - and with any significance? Well, at one point a working-class neighbor comes over, and Italian whose English is broken, and presents the McAllisters w/ his annual present, or tribute one might say, of two gallons of home-made wine (which Mr. McAllister immediately consigns to the basement), so we get a glimpse of the class relationships in this community. But what does McPherson make of this, do w/ this? Is Tommy troubled by the class disparities? By the condescension? There is no depth to these details, he makes no use of them, they don't advance the plot nor deepen our understanding. At the very end of the chapter Tommy imagines the scent of some kind of pastry, a currant bun?, I don't remember, that his grandmother used to make on xmas and reflects that he will never taste that pastry again - but it's just a sentence. Clearly, there's an homage to Proust here, as Proust wrote both about the evocative nature of taste and smell (famously) and about the death of his grandmother (extensively), but giving us so much more insight, feeling, reflection. McPherson just unloads the detail. Good for him, but why is this a novel?