It's very clearly visible on the Wine wiki that people who have ever seen Microsoft Windows source code cannot contribute to Wine due to copyright restrictions:
I guess the difference is that you can put in a weekend of effort on an Arch Linux installation and get a machine tailored to your workflow, few bugs, fast boot times, easy to maintain for the future, etc.
But no matter how much work you put into your Windows install it will be just as slow/fast, uncustomizable, and unoptimizable as it was out of the box.
At scale, yeah it does take a lot of people to do this. It has nothing to do with the type of app and everything to do with how business works.
At scale you have huge enterprise customers with complex setups and they want to integrate your fancy todo list app into their setup and will pay you tons to do it. Your fancy todo list app suddenly needs to have all sorts of security certifications, needs to guarantee some type of uptime, needs to be able to integrate with all sorts of systems and other products (some of which none of your current engineers will have experience with). A new device will be released (think Apple Watch) and you're leaving money on the table if you don't hire some engineers to put your fancy todo list app on that platform along with the 5 or 6 others it's already maintained on.
At scale, 1 in a million type bugs/problems come up every day and you need more engineers to deal with them.
At scale, you are generating and producing (and thus need to be collecting and analyzing) an amazing amount of data, which should be used to better your product, learn about your customers and try to grow your business into providing other products and services your customers want / need. All that data collection, storage, and analysis requires more and more engineers.
I just have no idea why this trend got so popular because in my undergrad CS program, we all had to take a database fundamentals class. And once you actually understand how databases implement transactions, rollbacks, atomicity, etc. and when you use said SQL databases and see how fast the queries actually are, how in the world could anyone convince you that a non-ACID database with no defined schema is better?
https://wiki.winehq.org/Developer_FAQ#Who_can.27t_contribute...
I think OP has a point here, personally.