Why does Storj use the STORJ token?

The Tardigrade customers pay in USD the SNO are retributed in USD per GB of egress or TBh of storage. So why are you using an highly fluctuating/speculative Storj token in the middle, with high fee cost for the Network and the SNO?
You could just send cash back to our credit card, it always pleasing to see a plus on our credit card which could be invested in developing our node or buying some crypto’s like Storj if we wish.