I prefer to use my skills on original content (that’s the place where I get satisfaction, gain experience and have fun with). Mundane, ordinary, repetitive assets are better bought. You see, everything is possible, everything can be made, the only problem is time. That’s why I prefer to spend my time making original (so only my game has it) content, and learn and gain experience from it.
Sure, I did make (when I was learning), a rock, tree or grass. But after I’ve learned it, I see very little point of making original trees, bushes and pebbles.
Identical point to reusing std:: library from C++, or boost:: from C++. During learning process, great, it is a fun to make your own vector or map or string. But you should use those provided by library writers in production code and not write your own from scratch, because as I’ve said, everything is doable, possible and manageable. The only problem is time (lack of it).
What is the difference between road sign bought in market place and one made by myself? The only difference is that instead of doing something challenging, interesting and original, I’ve spend my valuable time on making something bog standard, which I could buy for $20 instead and be done with it.