Private sector jobs will exist in any situation where there is a community with significant enough propensity for trade (population base / infrastructure existence) to facilitate it. Infrastructure does not “need” the private sector anymore than the private sector “needs” infrastructure. Without one, the other won’t exist. If one stops flourishing so will the other. Communities have been connected by roads for millennia. The difference between then and now is the quality and technology being used to facilitate trade and the security of those pieces of infrastructure. We need to continue to fund, as a community, any technology and undertaking which can (at a reasonable cost to the community) improve our productivity and facilitate trade. That’s how the private sector benefits.
Right now, as evidenced by pipeline hacks on the east coast, bridge failures in Memphis, utility disasters in Texas, and the potholes in your local neighborhood, the security (continued usefulness) of our infrastructure is failing, and that’s before we even start to talk about funding new infrastructure invention / construction to keep up with the pace of change. There are more than enough jobs that need to be done to make sure our private sector doesn’t begin to lag behind others. Government jobs just spread the cost of those projects out among all of the parties that will benefit from them.
Also, improving productivity of society is not just restricted to improving the health of physical or digital assets. It can include the improvement of the asset health of those doing the work as well. Making sure that a worker isn’t sick, or their house isn’t on fire, or their children are being cared for while they’re away is just as important as making sure the bridge that has a crack in it doesn’t fall down. Those things all effect productivity.