It's a habit I started back in my middle school days when I had a bunk bed that was in the corner of my room. Trying to make that thing is pure evil. That same exact bed is now in my daughters room. In the corner. Still just as hard to make. Have you ever tried to tuck in a sheet while sitting on it? Evil.
I have heard all the arguments about why making the bed is some sort of "necessity" but I don't buy them.
The "it just looks nicer and that makes me happy/inspires me/motivates me to clean/etc" argument. Do what works for you but for me it really doesn't make a difference.
See, we have this fancy device on our bedroom called a door. Once shut, the room disappears like magic.
I get up in the morning, leave my room and shut the door. I usually don't go back in there much during the day unless it's to put away laundry (or let's be honest, dump it on the bed to put away later only because I can't climb into bed at night until all those clothes are put away.) I just don't hang out in my room very much during the day.
I also don't show it off to company. Hey, wanna come hang out in my bedroom? That's something I haven't said in many years. Because that would be weird.
Some people prefer to climb into a made bed each night but I am honestly not one of them. It's one of the things that drives me crazy at hotels. Those tucked in sheets that don't quite pull up far enough. And they might as well be glued in there for all the good pulling and tugging and yanking will do. Annoying.
Why would I want to replicate that in my own home?
I know what you are probably all thinking. You know that if you don't at least sort of make the bed then that flat sheet gets all twisted and tangled. It gets untucked and pulls up off your feet. It gets scrunched up down at the bottom of the bed where you can't reach it.
My solution?
Ditch the flat sheet.
You know how after a night of wild drinking you wake up hungover. At least that's what I've heard. Not that I have ever experienced that for myself or anything. I've just heard rumors. 
me I was still too little and I would have to wait until I was older. I would wish myself bigger and dream of the day that I could wash the dishes all by myself. 
Every once in a while when my mom was feeling extra nice/insane/bored she would allow me to "play" wash the dishes in the kitchen sink. I would pull up a stool and fill the sink full of water. Then I would take a cup or two and she would squeeze a little soap into the water to make suds. I would splish and spash in the water and pour it back and forth between the cups. 
When the opportunity presented itself, and my mom was distracted by my younger sister or brother for a minute, I would add a squeeze more soap . . . ok half a bottle or so. Now I had mountains of bubbles! By the time she returned from changing my brother's diaper or pulling my sister back down off the bookself, I had created my masterpiece. I would be soaked from head to toe (bonus no need for a bath that day) the kitchen floor would be flooded (it needed to be mopped anyway) and there would be bubbles splashed all over the walls and counter tops. (I was thorough when I "cleaned!")