> all mainstream languages have eager evaluation models
That is incorrect, e.g. Java Streams (Javas built in library for functional processing of data) are lazy, which can surprise beginners. You say it's just an std lib and not a lazy programming language? Ok, the much older (but just as lazy) C# linq is directly integrated in the C# language, making the C# language both eager and lazy by default, depending on which parts you use.
Arguably Java streams aren't really lazy evaluation at the language level, because the programmer must use explicit lambdas around the lazy bits. Java itself is still eager.
That is incorrect, e.g. Java Streams (Javas built in library for functional processing of data) are lazy, which can surprise beginners. You say it's just an std lib and not a lazy programming language? Ok, the much older (but just as lazy) C# linq is directly integrated in the C# language, making the C# language both eager and lazy by default, depending on which parts you use.