Russell, a good question that comes up every now and then. 1/87 is also HO scale, and I understand how it is associated with model railroading. The scale is also huge in Europe for more than just model trains. I cannot tell you if there is a “what came first, the chicken or the egg” relationship, but 1/87 has a huge following for civil and military vehicles. Automotive model manufacturer Herpa’s magazine Der Mass:Stab is full of 1/87 dioramas with nary a train in sight. I have no doubt that toy manufacturers and subsequently model makers use the scale to piggyback with models railroaders would want to have on their layouts, but it seems like over the decades of his shifted into its own non-model railroading scale as well.
That said, why not just go to 1/72? Such is one of the modeling mysteries of model manufacturers and their chosen scales, such as why 1/35 and not 1/36 - or the established 1/32? I was pretty excited decades ago when - was it Hobby Boss or Trumpeter? - released some 1/72 Railroad models. And there are several model of manufacturers over in Eastern Europe that make trains in that scale, usually armored trains. But no great quantity of them
All that said, while 1/87 is no longer just a model railroad scale, Artitec does make model railroad models, so I suppose they are standardizing their products.