The short answer is that 99% of the time no purpose is being served by that cruft except to be bloat. Minifiers remove that cruft and optimize for the intended audience, which is machines.
The longer answer is that in optimizing for machines, you're also optimizing for humans in the long run. Anyone stuck with a 2G connection, dial-up, or Bluetooth tethered device, or a new ultra low powered device on a different CPU architecture, will appreciate not having to operate solely in the world of gigabit+ connections, 8GB mobile devices, or 8 core hyperfast CPUs. Realize that such use cases still exist, and for very legitimate, not truly edge cases.
Think of pages with hundreds or thousands of vector images. Not everyone can afford to run a Blink-powered browser or have CPU cycles for days. Every little bit helps.
Edit to fix typo and add further clarity.