Steam has a monopoly: yes. Steam, like apple, takes a cut from all payments in the store, and micro transactions. Considering how Steam is a company, and could just be evil, and bad, like Google, it's:

-Contributions and implementation of the opensource software Proton-Ge, which lets me just download a windows game and play it, off steam, and is also available, free & opensource on other platforms like Lutris. -Regular deals which make it the best place to buy games, if you choose to do so. -Steamdeck

Make it a (mostly) positive force, imho. However, a billion dollar company being able to do discounts below any small game distribution companies, is bad.