I generally use 2 as well, silent and non silent.

However, as common as they are, I sometimes need another. For example, I have a profile that is similar to silent, but with no vibration. This is useful in meetings, when phone is on wooden table and vibration is louder than ringing. It also tends to fall if on edge of table.

It is also conceivable that someone would like different sounds for alarms. Say, a discreet tone for reminders and a fog horn for waking up in the morning. Once could schedule "fog horn" profile from 6 to 8 AM.

It's still useful, IMO.