Why do games I'm ahead end up being called a stalemate?

A few times when I'm ahead I like to wipe out his pieces before focusing on checkmate and when I do this the game ends in stalemate.

Example: he had a king and a pawn. I took his final pawn then I got a draw. Even though I had a rook, queen, 2knights and 3pawns.

Because your opponent has no legal moves and is not in check.

Sooner or later you will realize that there are risks to your strategy.  

Maybe that day will come when you wonder whether another strategy might be more fruitful.

:) :)

just my two cents, but in chess as long as you checkmate, it doesn't matter what material ur opponent has. Once you have a clear advantage (i.e. promoted queen), just finish the game. Don't worry aby straggler pawns/pieces on the opposing side unless they pose a serious hindrance/threat. This finishes the game quicker, and u won't get stalemated.

Well, you have already found an answer to your query.

If there exists a point system on material left on the board upon one side winning, then chess gameplay gets trickier and weirder.

Hello beginner here. Hijacking this puzzle

I would say he should have played Rh2 instead of Rg1. Would have been mat no?

No.

because you're bad.

Your move #38 should have been Nc3 , ignore that pawn.

First you need to understand the difference between the 'Checkmate' and 'stalemate'. Checkmate is the situation where your king is under the check and doesn't have  any square to go. In the current situation Bishop is giving check to black king and all White's two rooks are covering other squares.

Stalemate is the situation where your king is not under the check but you do not have any legal move to play. In the current situation i made only one change, we have a pawn instead of Bishop. Now the pawn is not giving any check to black's king and black's king doesn't have any square to move because all are controlled by white's Rook. This situation is called stalemate and the game is ended in a draw.