Bear in mind, you may not care about a congressperson from Alabama, but the people in Alabama who elected him do, and he's there to represent those people... you have your own representative representing you. The fact that it's someone else's representative doesn't make them any less important because they aren't there for you personally.
And yes, Congress can effectively put someone on trial (see: impeachment) and the fact finding processes they use before creating legislation is similar to a court proceeding. You are legally bound to respond honestly.
The fact that Congress and the courts have different roles, doesn't mean lying to one should be okay and lying to the other should be illegal: Lying to both is illegal. Testifying before Congress is part of the process of sourcing truth for laws to be passed to address issues with our society. It's critical that people answer honestly.
And yes, Congress can effectively put someone on trial (see: impeachment) and the fact finding processes they use before creating legislation is similar to a court proceeding. You are legally bound to respond honestly.