I too am a buyer and if ebay put this into place and if was not compulsory I would just not use it - as it is too simple a concept to relay anything useful at all - so what I received it ?? but I am I satisfied with what I received ???

Satisfaction - that's the bit that really counts if you are customer focused and my goodness that's what the seller feedback system is for. 

It is impossible for it to be compulsory unless you restrict buying activities in some way and that would be madness.