These aren't children, they're young professionals just starting out. They are legally adults, they need to be treated equally to all other adults rather than put under specific restrictions just because of their age.
While it is true that many, if not most, people under 22 haven't fully launched yet, that doesn't justify the law as treating them as less than fully adult. Their not having launched is between them and their parents, a private arrangement between family members.
My mother does my taxes (Q: Why? A: Because she's a professional and I'm not.) but that doesn't mean it's reasonable for the law to require that people under 30 get their tax return signed by their mother. When my parents travel I help them find information on non-English websites, but that doesn't mean it's reasonable for the law to require that people over 50 get their travel arrangements vetted by a professional translator.
Experience-based restrictions? If you must. Age-based restrictions? Completely inappropriate, arbitrarily treats younger adults as subhuman, and violates section 15 of the Canadian Charter of Rights and Freedoms.
Please read the whole thing here.