It's all a matter of motivation.
I often write stuff down on the nav logs in flight, for example if we have an engine bleed problem I'll write all the engine parameters down on the nav log, and discuss them with an engineer on the ground. I also always discuss defects with an engineer before writing them up (if possible), as sometimes the way you write it up can make the difference between grounding an aircraft, or not. But, write them up I do.
However, the practice of not entering defects in the Tech Log to keep an aircraft flying, when it really shouldn't, is not acceptable in any situation. It does happen, and some airlines are worse than others; usually the smaller one with less resources.