It is due to the abundance of open-source libraries. To some extent it has removed the incentive for developers to re-implement closed-source libraries and they just want to use the library and get on with their product. The need to look at the intricate data structures or algorithms is always an excercise for the developer reading the technical implementation which is worth looking at but not a hard-requirement in getting the product out there (unless specified). I would say it was essential in the 1990s era (OSes, drivers, etc) but for creating web apps in 2019? I don't think so.

It is highly unlikely that a company asking me to implement a data-structure is actually going to use it or is explicitly using it. Unless they want to improve it in a research paper or fund a proof-of-concept that improves the state-of-the-art. My point here is that we as software engineers should know these DS and algorithms, but to companies who ask such questions in a interview, you should be prepared to use them explicitly.