Anyone with 5+ years of writing production code should be a Senior Software developer.

Then obviously you can say he is an average developer or a very good developer or a genius or whatever. I don't really get why developers should have different qualifications than other fields.

If you are working e.g in finance for more than 5 years you'll be prolly a senior something, what does it matter? Of course then someone can evaluate how good you are or not at what you do but thats it.

Now what makes a senior developer? Well someone that can take on a project and complete it from start to finish, for me is a senior developer or developer or whatever you wanna call it. Its very vague question, usually if you understand the whole lifecycle of a program and can understand the bigger picture then you are a senior software developer.