First of all you need to understand what kind of leak do you discuss:

Memory Leaks, Buffer Over Flows, Mismatched Memory Management leaks (etc).

Above leaks are most common - some of those are not really important, some can be absolutely crucial.

Some leaks are indeed false positive due to inappropriate settings of your environment or library you trying to debug (please refer to my last question).

For instance, major vendors like Tesseract or OpenCV tend to throw tons of false positive errors which should be just suppressed.

Also these errors are not really leaking memory or lead program to break.