I think because infrastructure is so critical to public health and safety (water/wastewater plants, bridges, buildings), we really want to make sure they get done right and that not just anyone is going out and designing these things.
The infrastructure I mentioned is an order of magnitude more...
I got my dream job by adding someone on LinkedIn that I met at a networking event. They weren't hiring but he messaged me on LinkedIn later when they were hiring and I got an interview and a job. All because I added him on LinkedIn after I met him.