"Are we rich because of hard work or luck?"

Translation: Apakah kita kaya karena kerja keras atau keberuntungan?

[XavierLamb9]

Why isn't "pekerjaan" accepted like "kerja"?

[Jon.Orble]

Yes, a common phrase for “hard work” is actually pekerjaan berat. Not saying kerja keras isn’t valid, just that there are alternative translations.

I’d actually say pekerjaan (formal) is a better translation than kerja (informal) in this sentence because it seems like a formal or poetic question to me, rather than something from regular conversation.

[angbagongquezon]

Father: son, having the spirit of hard work is already luck in and of itself.