Because your opponent still had a rook. The only time it is a draw when you run out of time is if the opponent has insufficient material to give checkmate eg.only a king or king + bishop/knight.
why i lost with more material and ran out of time instead of draw
when you run out of time there is no adding the points of whatever is left on the board. it's either the opponent has enough material to checkmate you by any series of legal moves or not. if yes, then the opponent wins, if no then it is a draw. it has nothing to do with you having more material than the opponent. that's not how it works. you can read the rules on the fide website.
The most mysterious thing in these complaints is this: what did the OP think about the clock in chess? Is it just decoration, nothing serious? If you run out of time, nothing happens?

im looking for an answer here too
Yes, you had sufficient material but that doesn't matter if you run out of time.
when you run out of time, the result of the game depends on whether the opponent can meet the conditions for winning or not. it no longer matters how many pieces you have left or which pieces. for all practical purposes, you cannot win anymore. the only thing that needs to be determined is if the opponent can fulfill the requirements for winning or not.
if this does not sit well with you then learn to manage your time. it is part of the game.
yeah , i know that im professional CS.GO and DOTA2 player over 14 years and i am not a good chess player but started to play chess as research about how gaming can effect human brain and kids

what did the OP think about the clock in chess? Is it just decoration, nothing serious? If you run out of time, nothing happens?
this comment made my day

yeah , i know that im professional CS.GO and DOTA2 player over 14 years and i am not a good chess player but started to play chess as research about how gaming can effect human brain and kids
most dota players reach 1400 very quickly in chess
yeah , i know that im professional CS.GO and DOTA2 player over 14 years and i am not a good chess player but started to play chess as research about how gaming can effect human brain and kids
most dota players reach 1400 very quickly in chess
im happy that you said most because im a tester guy test anything as possible

When you run out of time, you lose automatically UNLESS the opponent doesn't have enough material left to checkmate you.
If he only has a bare King, or King and Knight, or King and Bishop, running out of time is a draw instead of a loss. If he has a King and Pawn, he wins instead (because in theory the Pawn could promote to a Queen).
H! all this is my game and im new in chess.com but after i played i just got draw games when the opponent got more materials and ran out of time but when this happened to me i got 5 score more than him and i got queen king and pawn and he got king and rook some one tell me why when i ran out of time i just lost the game when i was ahead in score
Source: /live/game/8277880891 match id