As a software engineer, it doesn't matter how many programming languages are out there, you just need to know the ones you need to use. I only use 3 languages in general, but I know about 10 or so and the rest are too niche to worry about. If I have to use a language I don't know, it's going to follow mostly the same rules as one I already know so it's not much effort to learn enough to be able to work with it. The whole point of creating a new language is that someone is trying to solve an issue in a new way, so it would be pointless to require that it use some common syntax, you might as well use an old language.
There are plenty of tools to check for syntax errors. It can't correct them for you because it doesn't know what you meant. But there are also tools to correct formatting issues so that the code is easier to read and parse.
There are professional organizations, ACM and IEEE.
It's similar to asking why people speak more than 2 languages.