Maybe it's too scary or inappropriate for some people. That could be a reason.
Maybe because looking up certain manga can be a waste of time or not in line with your interests.
The main reason could be that looking for specific moments out of context might lead to a misunderstanding of the plot. Also, it takes away the fun of discovering things naturally as you progress through the manga.
Maybe it's too intense or scary. Some manga can have elements that are disturbing when you look at them.
Maybe it's because they can be addictive and take up too much of your time.
Looking at manga online illegally might violate copyright laws and hurt the creators.
It might be illegal and violate copyright laws. Also, the quality could be poor and not give you the best reading experience.
Maybe it's because some tattoos comics have inappropriate or offensive content.
Not looking up fiction could be because it can consume a lot of time and prevent us from engaging in more productive or beneficial activities. Plus, some fictional content might have negative influences on our mindset or values.
Well, it could be that looking at tattoos in comics might lead to misunderstandings or give the wrong impression. Sometimes the tattoos shown might not be representative of real-life values or might be presented in a way that's not suitable for all audiences.
Maybe the comments could contain spoilers that ruin the fun of reading the comic for yourself.