They want his firstborn for payment to repair it.
You don't appear to have children for you don't know what a first born or a fifth born cost these days but they certainly cost many orders of magnitude more than what it costs to replace a shoulder strap for a bc
The point is a BP + harness is about as simple as anything can get. Minimalist as it were.
And??? Does that make it "better" for EVERYONE for ALL situations? It doesn't at all. You need to look at the diver from a global system point of view not a microscopic point of view, there is nothing simple about diving or the diver's "system." It just differs when the "stuff" goes on the the parts of the system.
BTW, a wheelbarrow is far simpler than a Mercedes S600 indeed and has many less parts that may fail but they aren't the same and aren't meant to do the same job.
I own several BC's, BP/W and jack and back inflate, and I use each one of them for different purposes. I Definitely don't need a BP/W for single tank diving and it really doesn't add anything or is better than the others I use for single tank diving. Nothing at all. Heck, my SP classic can handle everything, including doubles, without any issues and is very comfortable. I now, after 15 years of extensive use, put it on the rack as a spare for the dive school simply because I had it for soooo long, and without any issues at all, and I wanted to try newer systems (I got bored with it frankly). The Classic Stab jacket is so simple, extremely durable, easy to use and mange and can work as a surface flotation device.