It's actually a very VERY good point. I've bought loads of paintjobs and ship kits now and yes, they do make for great screenshots ..
.. but, did I really buy them for that? (it would be like buying nice cloths specifically for selfies). And how many other players actually see (or notice) them? I'm forever flying in and out of Jameson Memorial, and there's always a few other players there, but they're inevitably inside the station (outfitting) or reading the mission board or somesuch. Certainly not gazing upwards in the hope of seeing my glorious ship go cruising past.
But then I think about cloths. How much time do I spend looking at my own cloths (there's certainly no 3rd person view in real life). Sure, other people see me all the time - but how may of them actually notice anything and how would I know if they did?
I think the purpose of these vanity items (like in real life) is simply to know that we're wearing them. It makes us feel good about ourselves. I'm not sure if it actually matters whether anyone is actually looking.