Why do prospective employers look down upon tattoo's in Britain?

I ask because i have tattoo's and would be very offended if i thought someone had turned me down for a job because of them despite my 2 degrees and other qualifications. I understand that if i had a swastika on my neck or a gang sign on my arm then an employer (much like everyone else) should frown upon it.. I have many tattoo's some of which i cant hide (neck, hand etc). Do employers seem to think that tattoo's portray a lack of intelligence?