The Revolutionaries were really just opportunists. They could have received the representation they wanted in parliament, however they saw the chance to start their own government, a new one, built by them, however they wanted. I'm not saying it was a bad thing that they decided to focus their efforts on starting a new government instead of working with their current one, but they didn't have to.
The Declaration of Independence was written to discredit parliament and the king (who, at this time, didn't have power anymore, it was already with the House of Commons), and to drum up support with other powers who didn't really like England (specifically France). They could have worked out a deal with the House of Commons giving them a representative spot, but their declaration explicitly decided against it.
Take a history class. You might get some context to the events you cite.