The reason to gate things behind skills isto make the skill selection important. Much the same reason as why you can't break things open, it basicly is the same as giving you free skills if you can ignore some mechanics entirely.
Agreed. Getting the ability to open locks, without paying for the skill, somewhat defeats the purpose of carefully choosing your character's abilities. It would be like asking to have a lot of free carrying capacity, without having to put a lot of extra points into strength. The choices you make while building and advancing your character should have consequences. As you say above, you shouldn't be able to ignore some mechanics entirely.
Although I suppose that there is some ground to argue for breaking things open on the basis of Verisimilitude. It just makes sense that you could blast open doors (as well as other types of barriers), if you have enough brute force. But then there is likely to be some tension between the goals of simulationism, and creating challenging game mechanics.