Yeah, most of your favorite artists got writers. The music industry is BUSINESS. Nobody at the top from the top executives to the top artists got time to goof around. As a BUSINESS it also means a whole lot of people are involved. A whole lot.
Think about how much money the top artists' successful songs and albums generate. People are definitely going to try and make sure those artists get as much support as possible. Think about how much goes on in between a song going from some lyrics on a paper/phone to audio distributed around the world.
When you got somebody who has the whole singing/performing/theatric lane and the FANBASE she does, you better make sure she has everything she needs to strike while the iron is hot and to keep that glow as long as she can (can be decades).
The FANS have chosen who they rock with and it wasn't someone else.
That said, this is why there are so many layers to typical 9-5 companies: you got people who handle where the money comes from, how it's split up, etc. Those departments take care of the specifics. When you're a songwriter, those layers of abstraction are now your problem. There are a whole bunch of things happening in between the Artist - Songwriter - Producer layers.
Think about the "Search" feature in Spotify, how good it works and how much money that feature is responsible for. Those software engineers probably get paid peanuts as well compared to how impactful that feature is and don't get invited into any award ceremonies for it either. Similarly, think about how many layers there are in the music/entertainment industry and how critical they are in making the content the common fan enjoys. Think of how much money the software like FL Studio, Ableton, Logic Pro, Pro Tools, etc. are responsible for. Songwriter is just a job like everything else but man, they often sound like they want everyone else's flowers. People like Roger Linn have built the industry, seen far less money in comparison and don't complain 10% as much.
I mean, does anyone even know who the person that made the TR-808 machine is? Probably some Electrical Engineer who made decent salary, but bet it's nothing close to the hundreds of billions of dollars his machine has generated and built the music industry of the last 40 years on.
Basically, this right here: