I'm always a bit confused as to why so many people think AFMUs are so important that you can't go without them. You can ditch them no problem, unless you want to go all the way to the other side and travel 65k ly+ - which is still doable without them mind you, but there its better to take it safe.
Factually, you are totally correct. AFMU not needed as in 'need = must have'
in no order of importance though, several reasons pop to mind:
1. The joy of exploring like an explorer of old - self sustained, live or die with what you brought. Some people explore for the belt notch of been there, done that. Some because we are weird an actually like spending weeks away 'out there' and enjoy exploring for the sake of it, not the bragging accomplishment.
for the former - the afmu is merely a tool, one perhaps they took as insurance on first noobie trip on whatever counts as a "long" trip. Then ditched because that tool is not needed to accomplish their goal, which was to get there and back.
For the latter, though - call it role play, call it extra ambiance, call it extra immersion, whatever. All I know is regardless of the weight, real mountain climbers carry 2nd propane kits. Despite the extra weight which Everest climbers will tell you in grams what they pack and don't. Because they know they are truly screwed if their one propane kit breaks or is lost.
now, we have zero consequence other than digital death if for lack of afmu it helped lead to our demise. But having one on board makes me "feel" like more of an Everest climber, an expedition to the North Pole pre- first flag landing. Hard to explain. You either understand or don't. Both are valid pov so no judging.
even if I never use it, I "feel" like it is more a true exploration voyage if I have one. Hence my reluctance to drop it out of my build.
2. Majority of players won't go farther than long range mission outposts outside the bubble, and the majority of explorers won't complete a sag A trip. I've tried twice and died - one I want to say wasn't my fault as I was testing how far pirates spawned in asteroid rings and died through experimentation. Other was my carelessness.
Point is there are a heck of lot more "junior" explorers than veteran ones who absolutely know the afmu is not needed vs junior explorers only "knowing". Until you have done it yourself, you don't really know it deep down in your gut, hence more people than not who post contemplating some build or another make afmu a "need" because logically, until prove to themselves - not just told - that afmu wasn't used to a deep trip, they will want to pack one.
3. Last - this one is just me. While I don't want something really major to happen, it makes my exploration trip a little more exciting if I actually had to use the afmu a bit. So I pack one. Hoping something minor but not deadly will happen. Again, makes exploration mor "fun" for me. So that is the last reason why for some th afmu is "needed" - because it is fun.