Why is there no garbage collection in c++

Garbage collection requires data structures for tracking allocations and/or reference counting. These create overhead in memory, performance, and the complexity of the language. C++ is designed to be "close to the metal", in other words, it takes the higher performance side of the tradeoff vs convenience features. Other languages make that tradeoff differently. This is one of the considerations in choosing a language, which emphasis you prefer.

That said, there are a lot of schemes for reference counting in C++ that are fairly lightweight and performant, but they are in libraries, both commercial and open source, rather than part of the language itself. Reference counting to manage object lifetime is not the same as garbage collection in C++, but it addresses many of the same kinds of issues, and is a better fit with C++'s basic approach.