I've noticed that many of the professional looking cupcakes don't have the cake reaching to the top of the liner. Do you think that is preferable to give it a professional look?

I think it's just a style. Flat, slightly domed, or a big hill.

My folks would feel cheated and feel it was a skimpy cupcake. They prefer a nice dome with buttercream.
A flat one is nice with fondant, makes a neater cover than a dome.