@Bob: Somewhat true, but I use BleachBit because it has more purpose then just cleaning files. It also has wipe features, like wiping free space to make files unrecoverable, and also shredding files on the go. I also help maintain Winapp2, which is a community made file that expands cleaning capabilities for BleachBit and other cleaners: https://github.com/MoscaDotTo/Winapp2/
Windows built in cleaner can't do any of this. Also, with BleachBit, it also cleans a lot of tracks on your computer that leaves fingerprints, which hackers/malware can use for quick access around your PC, so it makes your PC a little more safe and BleachBit itself leaves little to no fingerprints on your system, either.
But you are correct that usually cleaning out junk files is almost pointless these days due to not much speed gain and lots of people have 1tb+ drives now. I still do it because I like to keep my system clean and all.