Classic and Vintage Bicycles: What's it Worth? Appraisals and Inquiries - Rim-Hole Question?

This thread may be more appropriate somewhere else, but this is the forum that I follow most, so: This question might seem a little goofy, but I'm actually considering doing my first wheel build and I'm unclear about the different multiples of rim hole combination's. I have a set of Mavic Open Pro 36H rims and I'm looking for a set of 105 or Ultegra hubs to go on a road race frame. But I've noticed that most race bikes have a combination 0f 32-36, 28-32 or even less on the modern bikes. Is there a reason why you would want less spokes up front other than not needing the added strength as much and therefore added weight? Or is it more for the looks?

No; it's just that the rear wheel is more heavily loaded than the front and thus can benefit from more spokes. The old British standard for wheels used to be 32h front, 40h rear but by the late 70s the bean counters encouraged changing to 36h front and rear as that meant stocking fewer rim types and spoke lengths.

No rhyme, reason or pattern. Modernity seems to like the fewer spokes, the better.