Acrylic was what we were taught with back in school- because it was inexpensive. And I'd gotten used to it, and continued painting with it a long time precisely because it's cheap.
And because it dries fast. I'm admittedly impatient about drying time. Well, okay, and because gouache just never really did it for me. Gouache doesn't have the clear and pretty tones of watercolour/inks, nor the body of acrylic, and it just dissolves when you try to layer it up. Though, perhaps that was due to my lack of patience, too.
So throughout my design training, I'd stuck to my lumpy acrylics. I'd thin then into fake watercolour, and thicken them into fake oils.
I will be picking up oils at some point, when I decide my patience can handle it.