For most people, especially younger, pixel art is just a retro esthetic. Most indie developers do not even have the money to pay themselves, let alone hire an artist.
The way a lot of small indies get made is a group of people (often friends) with different skillsets work together and share the revenue. “Cofounders” in hn speak.
Friends working together generally only happens when they are still in school and have a surplus of time for projects that do not generate a consistent paycheck. As somebody with a lot of ideas and plenty of capable friends, my experience is that none of them are interested in doing unpaid work once they get on the job market.
When two people start a company, neither is employing the other, and they also aren’t working for free.