If you have a HOB
filter, like most folks do these days, you probably notice that the water dropping into the tank makes bubbles. This puts oxygen into the water. I have two ten gallons set up this way. They have no air pump and the fish are all fine.
Now, if you have a canister filter that releases the water down inside that tank (so that there's no surface agitation), you may want to put an air pump into your tank.
Also, you could put an air stone/bubble wall in if you think bubbles are attractive. I am thinking about putting a bubble wall on the back side of one of my tanks. Not because the fish need them, but because I like the way they look.