To be clear I don’t dislike PERT charts, and the story isn't that interesting. My office is trying to become more Agile and less Waterfall, but management only got as far as adding daily standups and were confused as to why that wasn't enough. I ended up explaining theory of constraints, lean, and agile to them and got drafted to help. There are a *lot* of teams and projects here (1k or so employees, almost all engineers or computer scientists, in our department alone). So the "hell" is being in management/planning more than doing (and with no authority to direct change, I'm more like an internal consultant).
PERT charts and Gantt charts (less useful in some ways, but a helpful visualization) are great from a scheduling and planning perspective. Interestingly, since this is largely a software shop, they ended up with an internal team that developed our planning tools over the years. They've never included PERT charts in their tools which might be something I'll point out to them. They do have Gantt charts (which can be generated from the same data), but these often don't show the same causal links between states/activities (the diagram gets noisy if you add all the connections in) so the connection is implicit (some activity is to the right of another activity in the chart means it may or may not depend on the activity to the left). What PERT charts we use are mostly handmade in another program and not in the main reporting tool that upper management sees, so projects have it but don't report it. Which is silly.