I've been thinking about this topic for a while. Ever since an interesting discussion with my mom on the topic of crushes. It seems that she and I have a very different conception of a crush, and a very different use for them.
To my mother, a crush is the first step of a genuine love interest. It doesn't seem to connect much to her imagination (I'd say that my mother doesn't have an imagination, but it's really more that she doesn't consider it imaginary). For someone married to have a crush on anyone would be, in my mother's world, a terrible sign for the marriage.
I view crushes entirely differently. Perhaps it's because I've never in my life had a crush on someone even remotely accessible. A crush couldn't be the first step of a genuine love interest, since there was no possibility of such a thing developing. My first crush was on a guy in my math class in middle school - a popular guy, though not the most popular - at a time when no one in my class would even talk to me unless forced by a teacher. I think the crush was engendered by Ben actually looking in my direction once. My second crush was on my boyfriend's best friend - not exactly available romance fodder. Especially not after his father was killed in a car crash, an event that increased the crush by making him a tragic figure, while driving it all the more home that a romance with me was the last thing the poor guy needed.
So for me, by the time I reached adulthood, a crush was firmly entrenched as someone to fantasize about, but not someone to approach. I viewed crushes as something entirely separate from my actual romantic life, and the pattern of having crushes on people who would be entirely inappropriate romantic fodder in real life has continued. Perhaps because of this my romantic fantasy life is pretty active, and has gone in directions I would never choose for my real life. By now, even were I unattached, developing a crush on someone would cause me to shear away from them, largely because my fantasy life has much in it that would make for truly lousy reality. Instead I use my crushes to explore things that I would hesitate (or completely avoid), bringing to my actual life and marriage. Safe in my head, well away from any real people, I can explore dynamics I can't explore elsewhere. I would never feature my husband in a rape fantasy (for example) - I know all too well that it's not something I would ever want in real life - but my imaginative world sometimes explores such things. When I tried to explain this to my mother, she didn't get what I was talking about at all.
Maybe it's odd of me. My mother doesn't see why anyone would waste time imagining things they don't want to have happen. To me it's strongly attached to my story writing. I want to be able to make sense of horrible things, and it's much better to do so by imagining the horrible things than by experiencing them. Frankly it's pretty hard to make sense out of horrible things when you're in the middle of them. You're too busy simply getting through them. Writing a story lets you do it in the third person. Crushes and a fantasy life allow me to explore in the first person.