They assume that they must be wearing the best blades and buy the same for their child. Unfortunately this is not the most informed way of buying blades.
Different blades suit different standards and styles.
Ask your professional for their advice. All professionals have their own favourite blades and ideas. If you do both you need an all purpose blade i.e. Coronation Ace, Four Ace, Coronation Comet. If you are predominately an ice dancer, you should be looking at a dance blade with a shorter heel and not so pronounced toe picks. MK Dance or Super Dance 99.