Development: new vs. ready-made

Together with Vadim, Andrey and Alexey we will try to understand why developers often write something new and not use the "ready-made". What factors contribute to this? There are many non-obvious things here: additional dependencies, the need for specifics, problems at scale, the difficulty of interacting with open source, the "free" nature of the ready-made, licensing restrictions, the need to constantly upgrade and others. Let's discuss what the pros and cons of cycling are, and where it's appropriate and where it's not. Get involved!