There was rationale behind putting those "standards" together, and I think it was real at the time, but I think it's fair to assume the rationale was based on the assumption you were standing in front of an unamplified chorus of people, or an orchestra, and you wanted to capture the whole ambiance of the room to some extent, and probably it was a beautiful room, and they taper got to set up in the perfect spot. I also think that the chief engineer at RCA (for example) wanted to set some standard for his company so that when they sat down to mix tape at RCA studios they weren't having everyone doing his own thing (kind of like us), and it gave them a standard, like all McDonald's Big Macs are the same, for better of for worse.
There are some scenarios where that is still valid... school bands and church choirs... maybe some folk groups or stage lip bands.
But mostly we are sitting in the OTS at a crowded room, trying to capture the 2 mono stacks blaring from a bazillion watt PA, and NOT capture too much ambiance (the drunks at the bar). You gotta do what you gotta do. And mostly what you gotta do is improve your signal to noise ratio aka music to chatter ratio.
I had some non-taper guy give us crap last night because we were set up roughly DIN... eyeball 90 degrees, and hand's width apart. He said we should be running at least 110 or 135. I said "I want to tape the band, not the bar". Everybody is an expert.