The question is whether that's a good thing or not; software adages like "Not Invented Here" aren't going to go away. For personal tools / experiments it's probably fine, just like hacking together something in your spare time, but it can become a risk if you, others, or a business start to depend on it (just like spare time hacked tools).
I'd argue that in most cases it's better to do some research and find out if a tool already exists, and if it isn't exactly how you want it... to get used to it, like one did with all other tools they used.