The enchantment glint on shields is as bright as the glint on tools, significantly brighter and stronger than the glint on armour, even though, like armour, shields are customisable in appearance, whereas other tools are not.

This leads to an enchanted shield looking out of place when used in combination with enchanted armour, and more importantly, banner patterns used on shields being difficult to see. This is a similar problem to what enchanted dyed leather armour used to have, until the enchantment glint strength for armour was reduced.

If the glint strength on shields was reduced, banner patterns would be more viewable.