It is mandatory for Sikhs to keep their hair uncut, Guru Nanak Dev ji said it and it was unquestionable after Guru Gobind Singh Ji made it part of our discipline.
However, it really makes me sad when people cut parts of their hair but keep other bits.
This is a bigger problem for the female sikh population, especially when it comes to eyebrows/facial hair. We, as sikhs, cannot remove ANY hair from the body. However, i can see why people do it (as i've done it many years ago).
If we are to be sikhs, i.e give our heads to the Guru through the Amrit ceremony, then we must live FOR Guru Sahib. I know it seems hard, but who cares what anyone in this world thinks.
When we die, they arent going to go with us, they arent going to be used as an excuse "I was thinking about what other people thought about me...". The only thing that will go with us is how much Naam Simran/Seva (Meditation/Service to Guru,Mankind) and how much we've erred in life.
It makes me even sicker when I find Singhs who say "I wouldnt marry a Singhni if she has facial hair", you wouldnt marry someone because of a gift your Guru has bestowed on someone? If Singhs think this way then they arent worthy or marrying sisters who have so much love for the Guru that they will keep their hair - to hell with what other people think.
If a Singh says that he wouldnt marry a female simply because of facial hair or other hair, than they arent worthy or being Guru's Sikhs. The Guru blesses us with kesh, but to us manmukhs it revolts us? We are the revolting ones if we think like this.