I agree with thesis but there are entire aspects of this that he didn't even touch upon. There is a multiverse of different billing nightmares for engineers.
I worked on a piece of software that bridged billing data from IBM mainframes out to the web. The hoops that had to be jumped through to get data out of the mainframes and the number of hacks and kludges involved was legendary. Likely everyone here has paid many bills in their life on websites that used that software. At one point I knew the vast majority of my personal bills had gone through it. Credit Cards, Utilities, Gas cards, etc.. Stuff everyone had to pay with paper before the web.
Basically the mainframes were almost incapable of any data exchange that was meaningful in the 21st century. Instead of IBM doing something same the market just built software to scrape bills off the mainframes printer output, which you could intercept in electronic form. But then every accounts bill files were different. And sometimes the mainframes moved data around on the page, and so on and so forth.
That gives me flashbacks. I worked on a payment system that had to pull data from third-party service providers that only made it available in the form of downloadable spreadsheets from godawful slow and unreliable JavaScript-heavy web portals. Just getting to the point of downloading the spreadsheets was painful enough, and then the spreadsheets themselves were inconsistent and would sometimes flap back and forth between two different formats for a few weeks as the service provider repeatedly deployed and then rolled back new versions of their software.
I worked on a piece of software that bridged billing data from IBM mainframes out to the web. The hoops that had to be jumped through to get data out of the mainframes and the number of hacks and kludges involved was legendary. Likely everyone here has paid many bills in their life on websites that used that software. At one point I knew the vast majority of my personal bills had gone through it. Credit Cards, Utilities, Gas cards, etc.. Stuff everyone had to pay with paper before the web.