Aerobars (especially clip-ons) take up a TON of handlebar real estate. This can leave you with little to no space to install your head-unit.

Some of these handlebars come with options for mounting computers, but many do not.

Fortunately, for about $2-5 you can make a simple (and lightweight - mine was 10 grams) mount for your computer that gets the job done, and doesn't look too shabby.