Rip CD to Mac - basic question

I have started to rip some of my CDs to disk using a mac. I notice a lot of people using software to do this. When I look at a CD in the finder it appears as a set of aiff files for each song, for which I have been doing a drag and drop onto my hard drive, just like copying any other file. I would rather not use iTunes.

My question is: is this a bit for bit perfect copy? If so, why use other software? If not, why not? Computer files are always bit perfect when copied. There must be some software intervention on the part of the OS anyway, as a CD doesn't contain aiff files.

Any help would be appreciated. I don't want to copy a lot of CDs like this and then find I have to do it call over again.