Software development is a lot about making good use of resources and if you reinvent the wheel for every job you do, maybe it isn't your cup of tea.

I've worked with developers who completely ignored good libraries and instead created their own terrible implementations. They got nothing done and what they did was a buggy mess that often needed months of patching.

Finding a good middle ground is the best way to go and when the loading time increases by only a few milliseconds, but the development is a lot faster and cheaper, that's a good compromise in most cases.