Share of income can hide much more important items, like absolute income. Most people care less about what share of national income they make and care more about what total income they make.
It's easier to have low inequality when everyone is poor. It's harder to keep inequality low when people as a whole, including median, get richer. It's also harder to keep inequality (say, by Gini) for larger populations. (As neat evidence of this last fact, 45 US States last I checked had Gini below the aggregate US Gini - it's how the math works, hiding nuances).
For example, from your graphs: US median wage is higher than Western Europe (very few countries higher, most decently lower) - so they have lower inequality, but the people have less income.
It's easier to have low inequality when everyone is poor. It's harder to keep inequality low when people as a whole, including median, get richer. It's also harder to keep inequality (say, by Gini) for larger populations. (As neat evidence of this last fact, 45 US States last I checked had Gini below the aggregate US Gini - it's how the math works, hiding nuances).
For example, from your graphs: US median wage is higher than Western Europe (very few countries higher, most decently lower) - so they have lower inequality, but the people have less income.
[1] https://data.oecd.org/earnwage/average-wages.htm