why some people offer draw even when they have winning position?
Probably the one winning does not think they are, and just offers a draw. Maybe they have some non-chess reason for wanting a draw to end the game, like someone arriving home perhaps? The only times that I offer a draw when I have a winning position (I will very seldomly offer a draw if I think I am winning) is if they are low on time (and I enjoyed the game) or perhaps my "winning advantage" is not enough to win (like a draw by repetition unavoidable, or something).
However, there is a greater chance that the one "winning" and offering a draw sees something that perhaps the opponent does not yet see.
The only way to really know, would be to ask the opponent why they offered a draw in the first place (after the game) ![]()