I don't care too much if the sheets are perfectly smooth either.
When I was single, I didn't use a top sheet at all. In fact, I didn't even have a bed, just slept on the floor on top of a mattress pad. Now, I could've easily afford buying a bed and mattress set but since it was just me sleeping on it, why bother? Once a week I would straighten out the sheet and blanket but didn't mess with it the rest of the week.
I guess deep down I'm a minimalist and prefer to keep things simple and functional. I have made it a point to travel light on my life's journey. Didn't see the need to get bogged down with a lot of material things.