Actually the previous poster with a peanut allergy had it exactly (but mine is because of my autism rather than a peanut allergy). It's about the set up time once I get to my seat. When I fly I need particular things accessible to me, often even if I haven't actually used that item on the last 10 fligjts. The idea that I might need to actually communicate with the person next to me to get to get something is horrible to me. Once I sit down, absent a desperate need to use the toilet I don't get up again. I avoid the aisle seat because people are always touching you on the aisle seat as they walk up and down the aisle. The window seat also allows a little more space to lean over to reduce the number of times you accidentally touch the person next to you.
So because of this, even as prepared as I try to be, I faff around a lot getting all of my stuff out. The amount of time I spend isn't normal - I fly a lot and I can see that I'm unusual. DH (if with me) just takes a couple of things out, puts his bag up and sits out.
Now if I get priority boarding there's no one around when I'm doing all of this. I'm not holding anyone up and no one is pushing past me. I always choose the back of the plane by the toilets so that I don't have a long walk up ti the toilets (again - inevitable touching of people), and that's normally one of the last sections to board (I fly long haul).
If I board at normal times people are constantly pushing past, interrupting, and I am an annoyance. This causes me to get flustered. This can trigger a melt down.
If I could get the same quiet to unpack by boarding last, then If happily board last. But I can't because then you're being rushed because they want to start takeoff procedures. Plus it would take longer for the airline - this is why slow people get boarded first.
So yes boarding earlier would make many people's lives easier as a preference because they like to board earlier / not have to queue / not have to worry about overhead locker space. My life would be easier for all those reasons as well. But that's not why I use priority boarding. I use priority boarding because it makes my life much easier if I don't have a meltdown.
Do I need to justify myself more to you? Or is there actually nothing I can say because anyone who doesn't have profound autism is always abusing adaptations in your book?
And whilst I've been pretty clear on this, yet again, if there is only one slot available for priority boarding someone with profound autism can have it if they want it. I can cope