VGからPVを削除できないのはなぜですか？

$ sudo pvs
  PV         VG         Fmt  Attr PSize    PFree
  /dev/sda2  lubuntu-vg lvm2 a--  <465.26g    0 
$ sudo vgs
  VG         #PV #LV #SN Attr   VSize    VFree
  lubuntu-vg   1   3   0 wz--n- <465.26g    0 
$ sudo lvs
  LV   VG         Attr       LSize    Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  home lubuntu-vg -wi-a----- <413.26g                                                    
  root lubuntu-vg -wi-a-----   48.00g                                                    
  swap lubuntu-vg -wi-a-----    4.00g  

$ sudo lvremove lubuntu-vg/home
Do you really want to remove and DISCARD active logical volume lubuntu-vg/home? [y/n]: y
  Logical volume "home" successfully removed
$ sudo lvremove lubuntu-vg/root
Do you really want to remove and DISCARD active logical volume lubuntu-vg/root? [y/n]: y
  Logical volume "root" successfully removed
$ sudo lvremove lubuntu-vg/swap
Do you really want to remove and DISCARD active logical volume lubuntu-vg/swap? [y/n]: y
  Logical volume "swap" successfully removed

$ sudo vgreduce lubuntu-vg /dev/sda2
  Can't remove final physical volume "/dev/sda2" from volume group "lubuntu-vg"

VGからPVを削除できないのはなぜですか？

ありがとうございます。