Your plumber probably tried to fix that clogged drain several times but the problem kept coming back. The clogging of drain is apparently a problem, therefore we need to find the root cause to fix this problem forever. Make people aware of not throwing stuff in sinks that would clog the drain in the first place. Clogging is a symptom, throwing stuff in sinks (it’s a behavior) is the root cause.
In business, we often try to fix things that would only take care of apparent symptoms. A falling market share, increasing production cost, decreasing competitiveness, increasing rate of employee turnover – all these problems could be faced with “symptom approach” or “root cause approach” for solution. The former will make the problem go away, only for it to appear again in future. The latter will probably take care of it effectively and efficiently. Which one would you follow?