If you are implying that a children's program that does not start at age 3 is in some way incompetent, I disagree. But it certainly can be a business reality that it's difficult to have enough ski school staff to offer a program that includes 3 year olds who essentially need more babysitting time than ski instruction for a full day of ski school. Especially in regions where parents are not necessarily good skiers themselves.
The situation for staffing ski school is very different in regions without a concentration of big mountain ski areas/resorts.
I rather agree with you. I just don't think it's fair to blame the child's maturity.