why a draw?

Fifty-move rule.

Your last draw on September 12 was because of the 50 move rule. When 50 moves are made without a capture or pawn move, the game is drawn. The clock started at the beginning of move 60 and ended at the end of move 109. In order to avoid stalemates like this in the future, work on basic checkmates such as King and 2 major pieces vs king, King and Queen vs King, and King and Rook vs King.

In the game you eventually did what was necessary by driving the king down to the first rank. Your key error was 71...Rh1+ that allowed the king to escape to the center. Instead you had two options to play for mate. Your quickest was 71...Na3 72.Kc1 Kd3 73.Kd1 Rh1#. The slower way is to play 71...Rg2 72.Kc1 Kd3 73.Kb1 Kc3 74.Ka1 Kb3 75.Kb1 Rg2#. By losing that tempo, you force the king to either move away or get mated. Eventually, white runs out of moves and gets checkmated.