Generally, employers don’t like that their workers or future employees have tattoos. Applying for a job, even going smartly dressed, if the enterprise doesn’t agree with this kind of way you will never be engaged.
Evidently, there are jobs which don’t need that the worker has a good image because they don’t have direct contact with the public. But even in this case the enterprise watches over what their workmates will say, who can claim to the boss the situation.
Would be it considered a discrimination against people who have tattoos on their skin? There are worst things! You can be the best worker in the world, with your studies and marks, but if you have a tattoo you will fail the policy of the enterprise.
A lot of enterprises don't have no visible tattoo policies, which is why many people have hidden tattoos or in less visible places of their bodies, because if the boss knew about they know that will be fired if discovered.