That's a good question, ii3rittles. It all comes back to comfort; often, it is easier to do nothing and dream than it is to actually carry said dream out. The accomplishment of the dream requires effort, work, time and choice. Choice is the hardest motivation.
If I leave it a dream, it is perfect and pure. There's no lopsided portrait trees, decks that slant or mistakes to be fixed. In the dream, I didn't have to make six nail holes for one nail, trying to get the frames straight. In that dream, I did it perfectly.
Many of us put a lot of stock in how we are seen; I don't like to be seen as a failure, so, more often than I'd like, I stick to what is safe, what I have an aptitude for. This is not healthy, but is a sacrifice my pride feels willing to endure as my mind's eye says I'm perfect. I so desperately want to be a great Dad, not just a good one, but there are things I have to do to make that so. I want my kids to look up at me with pride. Messing up, makes me feel like a failure, so if I stick to what I'm good at, then I won't disappoint them.
And then there's laziness. I'm too comfortable on the couch, the game's on, I only have 16 hours of awake time, I can dream it better...
I hope this helps.