Needless wiping/overwriting of the data, would be more problematic for flash drives. The heads of the hard drive do not touch the surfaces (until bumped when running) The magnetic materials can change back and forth endlessly. Hard drives generally, die in an early stage of life (defect) or they live as long as the moving mechanical parts of them would survive for.
If the computer/drive is not treated carefully , and you have needless writing, the head is over the data area more often, it would increase the (slight) possibility of it getting damaged when abused. If there is no UPS for the computer, it would increase the chances of a minor corruption on power loss, doing unnessisary writing.
On the other hand, depending on the OS , something like windows can be writing all the time needlessly, so who cares, it would not change anything :-)
Once the clusters are marked for deletion, they will be overwritten soon enough , when new data comes in and writes into those spaces.
Overwriting 7 times is overdoing the whole idea, doing a single overwrite on a stable system, should not change any life expectancy of the drive. One overwrite is enough to hide the data even from higher end recovery or forensics.
A user might want to have a Balance of security , You would not be able to recover something you accidentally deleted/cleaned yourself. How many times does a person make misteaks vrses how many times other people are trying to mess with them.
In a journaling os (leftovers), and with so many things being all over the registry, and with many index.dat files that dont clear easily, layers of caching, if you really need to hide everything, its going to take more than Ccleaner :-) With a few hours on a system that is fully "cleaned and secured", I can find layers of breadcrumbs they left all over, without me even trying to seek them out. New programs and ideas and updates adding in new yet cleaned items , the process of full hiding best be done with a degausser :-)