Part of the reason that PSU issues are less of a problem now is that, to some extent, they were just cover for a couple of actual flaws in the original Raspberr

Part of the reason that PSU issues are less of a problem now is that, to some extent, they were just cover for a couple of actual flaws in the original Raspberry Pi. The first screw-up was that they misread the data sheet for the USB hub and Ethernet chip they used and backpowered the entire 3.3V bus from its regulator, causing it to overheat and fall over. Since this caused every method of communicating with the Pi to fail the only solution was to reboot. (Not all boards were affected, it only happened if the voltage of the internal regulator was higher than the external one and every chip had a slightly different voltage.) The second screw-up was a USB driver bug which caused it to send commands to the USB hub at invalid times if a full-speed or low-speed USB device was connected. Basically every USB keyboard and mouse on the planet is either a full-speed or low-speed device. This caused input issues and even complete hub lockups which were blamed on the keyboards and mice drawing too much power or users connecting an underpowered PSU. In reality, the Pi as originally released was incapable of reliably supporting pretty much any USB input device.