I think "server-side projects" is maybe too broad a term. Yes, there are plenty of server-side software where concurrency pervades the codebase. But if you're making a web app, for example, it's common for all of the code you actually write (the "business logic") to be single-threaded.

Things like the core request loop and the DB connection pool will need to handle concurrency, but a few people will have figured out how to get that stuff working and you can just use their libraries.