For 60% owners, what is the appeal of using it? isn't using the F keys harder and no arrowpad makes some games hard to set up
Better ergonomics as you need to spread your hands less compared to a full size or even TKL keyboard. Programmability means that nothing is really lost. While the Vortex Pok3r (the bare minimum pre-assembled, mostly programmable 60%) can not do numpad scancodes, all other programmable keyboard can if you have a game that uses them. For arrow keys you can again program them to where you want them. I replace the bottom right corner modifiers with arrow keys normally because I never use those keys otherwise. Other typical option is Fn+IJKL or Fn+WASD, obviously a bit awkward for games that use arrows for movement etc.
Using function keys is actually easier because you don't need to to reach further than the number row or whatever you want to use for them. A pretty common option is to replace the Caps Lock with Fn key which makes Fn+number very easy to do. I'm currently playing Deus Ex Mankind Divided and have no problems using the function keys in that.
While getting used to a 60% takes some practice, once you get comfortable with it it becomes second nature and you won't miss dedicated keys for many of the keys you probably didn't use that much in the first place. I mean I don't even have Caps lock or Insert mapped on my keyboard because I never use them.