Of course aware is unnecessary for the user, unless that ad enables you to use the app without paying a license fee. These guys spend a lot of time developing the apps. Nothing in life is free. If they can subsidize their development with aware and keep the software available without expense to you, you should be happy. If you like the app, but not the adware, buy it.
I still haven't found an app that I feel is worth more than a couple bucks. A well done popular app at even $ 2 should easily generate enough income to support the effort. I used to program in a previous life for a fixed salary. What they paid me could not have kept me programming. It was the adventure, man versus machine. When it worked right, it was a beatiful thing.
Give these guys some props.