At lest in web development, the website is always changing thus so is the code. Therefore the maintenance burden favours bespoke code over libraries as the form

At lest in web development, the website is always changing thus so is the code. Therefore the maintenance burden favours bespoke code over libraries as the former is easier to adapt to changing requirements. However ultimately in reality a decision based on product ownership culture, when it’s more important to produce results now ( velocity) rather than in a few months time (maintainability). It’s hard to change culture.