You can both fight over this, but its pretty much useless. Both Sides are right. If you are on a low resource computer than your going to need a cleaner/defragger to clean up the system. You need this, because as twitch said config files and other crap is left behind and trust me a lot is left behind.
On the other hand if you have a high resource computer you wont need a cleaner or defragmenting tool. It also depends on what the user chooses to do. If he would like to save some space and get the little bit of performance boost he/she could then they have that choice. If they could care less, because there comp is more than enough then they don't have too.
Also, about the ext4 file system it may be slightly superior in dealing with fragmentation, but if you install windows on SSD it will be just as good as the ext4 format.