That works for certain things but for some creative works there is no one offering enough money in one chunk upfront to make it worthwhile. Not that people only seek profit but people have to eat ultimately.
The work takes time and energy, often hard costs as well. These can be offset but spread over a number of years. It's just a different model but without it we wouldn't have some of the works we have today.
Take software for instance where both can happen - I can be paid to write an application and boom, done, money in the bank. Alternatively I can have a share in the proceeds - I invest my time and energy for no immediate payback but eventually the ongoing revenue makes it worthwhile.
Same with photography - you can be commissioned to take pictures (e.g. weddings) or you can go round taking pictures and hoping to sell them as stock images and over time generate revenue so you can keep doing it and paying for equipment etc...
Without copyright you won't have many creative works.
I work for my money, and an artist deserves money for his work too. The earnings of my work of today are however limited. My boss doesn't pay me next year for the work I do today
But you likely get paid substantially more *today* vs someone who's earnings are spread over possibly decades. It's not like they are being paid your salary over and over. They rely on the protection of copyright to provide the earnings for the time and effort they invested.