I'm not a web developer and I'm not scared of C, but I very frequently find that optimizing the JVM is much easier than writing a similar piece of code in C for my real world problems.
The short answer for me is all the great tooling that comes with a JVM solution as well as the simplicity of deployment. Getting a C/C++ native solution to play nice with a continuous integration environment is often very painful (especially compared to a system that is JVM only). Unit testing tools are better for the JVM, IDE/Debugger/Profiling support is better, etc.
All of these things (and the fact that good JVM code can be very close to C/C++ performance) means I don't roll with C because it's scary, rather because it's a pain.
The short answer for me is all the great tooling that comes with a JVM solution as well as the simplicity of deployment. Getting a C/C++ native solution to play nice with a continuous integration environment is often very painful (especially compared to a system that is JVM only). Unit testing tools are better for the JVM, IDE/Debugger/Profiling support is better, etc.
All of these things (and the fact that good JVM code can be very close to C/C++ performance) means I don't roll with C because it's scary, rather because it's a pain.