Does a SLR camera need a flash?

My answer is collocation! Use a flash when shooting in backlight, and the built-in flash can't be turned on. Be sure to use an external one, and take pictures at night. There is a limit to adjusting ISO alone, and the adjustability of low-end SLR is poor. At some wedding banquets, you have to use it, so it's a question of early matching and late matching, not a question of matching and not matching.