The Government was elected on a manifesto which made clear the transition period would end on 31 December 2020. This is now enshrined in primary legislation and it remains our policy.
Extending the transition period would simply prolong the negotiations, prolong business uncertainty, and delay the moment of control of our borders. Extending the transition period would mean we will have to make further payments into the EU budget. It would also keep us bound by EU legislation, at a point when we need legislative and economic flexibility to manage the UK response to the Coronavirus pandemic.