First of all, I like books and read them often, so I do like "text based" stories.
And so ? You aren't the only one who like to read, I try to read at least one book/week, and when I was younger, having more free time, it wasn't exceptional that I read at least one/day. Still, I prefer Visual Novel when it come to games here.
As for why I like VNs there're two main reasons.
Please, don't take me wrong, I'm not criticizing you, and it's not "against you". It's just a question that pop my head while reading your explanation, why do you like to read if you are so bad at it ? Because it's what your two main reasons are saying, you aren't good at reading books, or perhaps is it more "you are made for it".
The reason why people generally complain about movies adaptation is because they rarely match what they imagined. The characters in your head are not precisely what is described, they slowly derive from the description to become something unique, tweaked by what yourself imagine from their actions. And, of course, the tone and mood are only set by words. Whatever how good the author can be, you are never totally sure that you read them correctly.
This make the story unique. Every reader have read a different story with different characters, and actions taking place on different locations. All those stories have in common the canvas woven by the author but, anything build following instructions, they aren't faithful to the original intent, having a part of you in them. And you are saying that you like text based stories precisely because you don't have to do that.
Of course, the same could be said for me. After all, as I said I prefer Visual Novels, therefore to be shown what the characters and location looks like, and what the tone is. But unlike you, who said that you prefer when you don't have to imagine them, I do it because I want to continue to use my imagination despite the (too often) lack of writing capabilities of the author. I want to read the tone and mood from the combination between the not so good dialogs and what the image in front of my eyes is telling me. I want to see what the bedroom looks like, to be able to imagine what the character is doing inside it, and so on. Since I the lack of writing capabilities don't permit me to goes behind the words, I want to at least have the possibility to go behind the images.
Now, perhaps is it just because, after a bit more than 35 years spent reading so much, books start to be annoying and I want a new challenge. I don't know and it's not really the place for such introspection. But the fact is that there's really few authors on the adult gaming scene, and more generally on the gaming scene, who effectively have the capability to make me dream with just their words. And it was already the case in the mid 80's, when the games that made me discover video gaming and like it where mostly textual. At this time they weren't near to the books I liked to read, and it haven't really changed nowadays.