Because they think they are smarter and wiser than our Founding Fathers, and because they think their agenda supersedes all other considerations.
No, they don’t think they’re smarter. They have an agenda and they aren’t going to let a little thing like the constitution get in their way. They are power hungry and have great disdain for our American way of life, which for the life of me I can’t understand why. But whether it’s the Supreme Court using foreign law to make decisions, or Obama with his czars, or the Congressional Democrats and their unconstitutional tax laws that they pass, the constitution is an impediment, so they ignore it.