I think the reason comes down to differences in values.
Values are the measuring sticks by which people quantify success in life. Whether or not we realize it, we constantly measure our actions against our values, and how we 'measure up' determines our self-worth.
If I had to guess, kindness and compassion are core to your values. As a result, when you see a greedy person, you feel disgust because you would feel worthless if you were in their shoes acting in such an unkind/selfish manner.
For better or worse, not everyone holds the same values. For example, some people value 'winning'. Individuals who value 'winning' want to be the best no matter what. There are many ways to measure the value of 'winning', but money/material possessions is one scoreboard/metric. If they accumulate more of it, they feel more self-worth.
Why do people hold less 'wholesome' value sets?
Are certain values less worthy of others? Should we pass judgement on people who hold conflicting values?
These are interesting questions. On the topic of 'why', I'd expect environment plays a major factor. If you're brought up in an isolated bubble of wealthy individuals, it's quite easy to imagine how one would grow a value attachment to the associated luxuries.
Personally, I don't think there's inherent value in anything. As a result, no one value is 'truly' better than another. However, some values drive actions that harm other people, and those are worth passing judgement from a utilitarian standpoint.