It's about troubleshooting. When you have a complex infrastructure, it's not enough to say that your db queries are slower than usual. Ok, so you immediately see that your db server is getting a lot more traffic. What was the root cause though and what can you do about it now? Given enough "funny charts", you can see for example that you have hit a resource limit that you can temporarily raise and also see that a particular component of your infrastructure has an anomalous behavior, e.g. a cron job that was usually utilizing resources for a few seconds, now takes minutes. So you can provide a quick workaround and move on to investigate what changed with that cron job.