RetiredF4 wrote: Computers and all other stuff built in to modern FBW aircraft donīt either, but they are deemed necessary anyway. Because they help and assist to implement airamship and flying skills, as an AOA indicator would do as well.
Otherwise we could argue about what is really necessary besides airmanship and flying skills:
A cup of coffee: When the coffee leaves the cup, you are flying upside down.
And a cigar: When it is finished, itīs time to land.
AOA indicator necessity is a function of aircraft handling qualities and mission. It is neccessary in F4 where above 15 units AOA you start using pedals for lateral control, and approach using 19. Otherwise you may depart its operating envelope. In A4 you need it for carrier landings, but don't for airbase operations, although it could be more accurate than airpspeed for determination of climb airspeed, cruise airspeed, endurance airspeed etc...
If it were mandatory, it wouldn't be offered as option, e.g. most Boeing passenger transports. Like ashtrays.