Why do presidents feel the need to defend all government laws, when those laws are thrown out by judges? Why not just let the lower judge's decison stand or let some other group defend the laws?

Right now, President Obama is forcing himself to defend the Defense of Marriage Act, even though he’s against the Act.

There is no Constitutional requirement for him to defend the act. He is only defending it because it is “traditional” for Presidential administrations to defend all laws passed by Congress.

So why bother defending it? Why not let the law lapse as the judge ordered? And if some Church or other group wants to defend the law, let them do it?

Why does Obama feel the need to follow a stupid tradition?

Or is it not stupid, and would there be negative ramifications if Presidents started to just let judicial decisions stand, instead of pushing for one way or the other?