What? Operating systems are big projects and the tools to write them safely (and open source) haven't existed for very long, so it's a question of manpower and effort not technology. C has almost no performance benefits these days, either, due to advances in compiler optimization; if anything it can be less as other languages can provide more static guarantees to the compiler to use when optimising.

That network stack written in C gave us heartbleed for example. If C arrays were bounds checked by default (e.g. they carry around their size), this could've been easily avoided at no runtime cost.

How can you honestly complain about people wanting more safety in software? If it's speed ("high performance") then you're probably implementing yourself in C (e.g. Bounds checking) something that is built in either at runtime or even statically as can be done in some cases.