The reason is give time to Trump for prepare your defense .

       The House will deliver the impeachment article against former President Donald Trump to the Senate on Monday, formally launching trial proceedings next week, Senate Majority Leader Chuck Schumer said on the Senate floor Friday.

                     Schumer’s announcement comes after a request from Senate Minority Leader Mitch McConnell to delay the trial until February and give Trump and his still-forming legal team time to prepare a defense.

                    The House will deliver the impeachment article against former President Donald Trump to the Senate on Monday, formally launching trial proceedings next week, Senate Majority Leader Chuck Schumer said on the Senate floor Friday.

                  Schumer’s announcement comes after a request from Senate Minority Leader Mitch McConnell to delay the trial until February and give Trump and his still-forming legal team time to prepare a defense.

SOURCE ABC NEWS