I can say that if I wanted to read more than to play, I would read a novel.
The reason I play IF games is because I enjoy the interactive part of it, a lot of the games here and other sites that I love to be would be big ass noes if they were an actual book instead of an IF.
Mind you, I do love reading, but to me IF and books are completely different experiences, the fact that their medium is that of text doesn’t make them even similar to me, the same way that some people love watching movies but can never get into shows.
Now, with that said, I feel like contrary to what you seem to think, most people that plays these sort of games are here to play, not just read.