Will you please explain the reason why winning a game is worth different points depending on how many continuous games you play one person? In other words, why isn’t winning a game worth one set amount of points regardless of how often or the rating of the person you play?

Last night, I played someone 8 or 9 games and won all of them. By the 4th game or so, I was earning 1 or 2 points and the last two or three, I won nothing. In this case, my overall rating was much higher than who I was playing. However, a few months ago I was in the  60s playing someone in the 200s and as the number of games progressed, the number of points I won decreased as well. I am sorry but it is a big deal for a 60 player to beat a 200 player several times in a row and yet my rating barely changed...and neither did hers. 

A game is a game, a win is a win, fair is fair. I am interested in understanding the thought process behind manipulating the numbers in scoring. Thanks ahead of time!