Then you have lads who use python who can use virtualenv, and then the ruby ones who use rbenv and then you have the CPP developers which are usually fine but on Tuesday Joe messed up the linker settings and all of a sudden we're not statically linked, thanks Joe.
And then our Java team forgot to tell the sysadmins that they upgraded the JVM version.
The thing with docker is that you just get a complete package with everything delivered directly by the developer and it's very hard to mess up.
Also docker can run applications that aren't shipped by people in your company and also does more stuff (like more sandoboxing and it also helps you with the resource management).