A lot of people of people are afraid of flash. Flash is much more complicated and much more difficult to control because there are more parameters. Plus note of how many bad flash photos: the deer in the headlight look in a cavern.
One of the major problem is that people do not know what controls flashes:
|ISO sensitivity||ISO sensitivity|
|Distance from flash to subject|
|Flash output power: full, ½…|
|Flash accessory: umbrella…|
This applies to all digital cameras, not only to Canon EOS flashes, but Nikon, Pentax, Olympus…