However, helper apps can be a bit of a pain. First, they have to be installed and then configured. Installation is probably manageable, but configuration is a bit technical and unless done correctly, the helper application won't work. The other reason why some people don't like helper apps is because they force another window to be opened. Through this other window you can then click play to listen to the audio.
Helper applications are still good for some purposes, however.
First of all, if you are using Netscape 1.x for some reason, you have to use helper apps because plug-ins won't work. Secondly, in some cases there may not be a plug-in for the particular kind of file you want to view, listen or see. And, occasionally people prefer the helper application over a plug-in because it works better or more efficiently. This can be particularly true with video or audio. Plug-ins work by looking at the file type.