Earth Ponies don’t have a nobility technically. Their version of nobility are powerful buisness leaders.
Unlike Canterlot nobility which has a reputation for being lazy, these buisness leaders are encourged to be hard working to increase their buisness.
Even if Spoiled Rich is well spoiled she actually despises Canterlot nobility even if their fashion was superior. She believes in meritocracy (or at least she claims so) where talent is considered far more important than one’s royal blood. She blames blank flanks for being lazy, and encourages her daughter to have a strong work ethic as in newspaper publishing or entrepenurship. When somepony accuses her of being spoiled, she angrily points out her contributions to Ponyville, like its education, whether or not she really helped or not.
Diamond even used to justify bullying blank flanks because they just “didn’t work hard enough”.
Of the three races, Earth Ponies have the most obsession with cutie marks especially since they’re considered the hardest working of all the pony races.