We come from a billion+ years of organisms that have had to strive and fight for everything. Not necessarily all the time; there are brief times when resources are free and easy for some species (like, "a disease kills of 95% of your species and you're the only thing around that eats grass" or something; for the survivors it's suddenly a cornucopia), but they don't last this long, nor are they ever this easy. It's not hard to see why our genes haven't really prepared us for this wealth.