Not failure, it just tends to be a bit half-arsed. The things the gov't tends to run well tend to be things where a) there really isn't a private-sector equivalent to compare to and/or b) the people in the job are not driven to work primarily for the money.

Most public-private comparisons are generalizations, the government is not an awful bureacratic mess, our bureacracy is actually very good at it's job. Private industry is not an unbounded pool of innovation where bureacratic BS nevers interferes with efficiency and improvement.

Still, by and large the gov't tends to not so much muck things up as slow it down and leave it a tad bloated. Risk is bad. So riosks are avoided, because the gov't bureacracy has a legitimate fear not just of being made scapegoats of some minor disaster they aren't to blame for, but actual real disasters they are at fault for. Walmart does not have to worry that a minor and unnoticed flaw in a new shipment method accidently resulted in a brigade of soldiers not getting a shipment of munitions or food. Ironically, walmart does use some logistical methods copied from the DoD. Besides the politics and fear of angering someone powerful by damaging their 'ricebowl', gov't employees tend to have a real and legitimate fear of innovation because when it goes wrong it is often a disaster, and because it is the government, a real chance of a runaway witch hunt. For this reason it tends to mean that everyone involved at every level is leery of risk, and since everything has to run up a long chain, someone is likely to get jittery about it along the way and kill it.

Then there is funding, most departments have a 'use or lose' situation. If they don't spend their whole budget, someone will cut the excess, if they do spend it all they have a good chance at getting more next year. So they have no incentive to try to find cheaper ways of doing things. That can happen in businesses to but not so much. Overall it just makes the government fairly bad at running things, well, not very bad, just not as good, like a fat housecat, it catches mice, but with less skill then a leaner cat and less hunger-incentive to try, there's always a bowl of food in the kitchen after all.