Why most players such as Messi, Neymer, and Ibrahimovic have tattoo Cr7 as he is called doesn't have any tattoo, reasons are due to the fact that he usually donates blood and bone marrow although having a tattoo doesn't prevent one from donating such things restrictions are advised and observed by blood donations facilitators.
The Red Cross for example, advises that individuals wait 12 month before donating after having a tattoo especially in a state were tattoo studios are not regulated.
Blood donations organization in the united kingdom generally advise blood donor to wait for 4 month after having a tattoo or piercing before giving blood, The formal Real Madrid star uses his Instagram and Twitter account to promote the cause of donating blood, in particular, Ronaldo has championed the "BE THE 1" an organisation which encourages people to donate blood and plasma.
Which players have tattoo
While Ronaldo has thus far eschewed having a tattoo, it remains a popular form of expression among high profile footballers.
Ronaldo's nemesis messi has a number of tattoos around his body, on his legs, arm and body which he dedicate to his loved ones.
David Beckham is another popular football star who also has numerous tattoos on his body.

They are only 2 footballers on earth Ronaldo and the rest. if Roanldo was a religion many people billions of people could have converted.