I'd love to give the HLD a try in the future as well. Need to get the basics more on lock first though lol...
It seems most strings are made a good bit thicker than they technically need to be, if the only goal is to avoid breakage. With some modern material options you could really make a string thinner than regular household thread... but that wouldn't be very comfortable on your hands to shoot, and would definitely eat up the nocks without a ton of padding in those areas. That's an extreme example obviously. My guess is that stings usually have more strands than 'necessary' due to the fact that its just easier to overbuild the whole thing a little, than to go through the trouble of padding up the loops and fiddling with building up the serving area a ton. A bit of extra material is also providing some long-term durability if some of the strands get damaged. There's also a bit of a look and feel factor as well. I definitely wouldn't like the look of a tiny thread size string on my bow, even if I knew it could handle the stress perfectly well.
Most of the strings made from natural materials are very thick in comparison to 'thick' B55/FF strings. I'd be willing to bet that when people first started transitioning from sinew/natural cordage strings to synthetic strings, they made the synthetic ones even thicker than we do now just because that's what they were used to. There's definitely a happy medium somewhere between look/feel, ease of manufacture, and performance. I'm sure a thiner, padded up string, gives a slight increase in FPS... but my shooting definitely isn't to the point where I'd need it or notice it