Older cheaper voltage regulators are typically more like 2V drop and the optimum input voltage is somewhere around 7-9V for a 5V output. In practice a lot of devices used 9V power supplies because that was the lowest widely-available voltage that met the requirement. More modern LDO regulators would have plenty of headroom on plain 6V. It'd be kind of unusual for any electronic device to need the extra .2V in this particular case.
It's a great old school design, but there are somewhat newer capless designs that are about 2 drops like the LM2940.
There are a lot of other designs between a 0.2V current feedback pFET design, but not all of them have been so popular that their costs are close to packaging.
