The intent with professions is that you can only have two
Err, those of us with the Master Of All
achievement would respectfully suggest that the intent is clearly not developer-wide ;)
Over the years a number of things have changed and lessened those interactions based around professions, but probably none more impactful than alts. With good intentions to help people catch up to the end-game, it of course allows for people to have more alts with more professions, which in turn reduces reliance on others and shrinks the reasons you have to interact with others.
I interact with others ALL the time. I make stuff free of charge for people asking in Trade chat. I make stuff for guildies. And yes, I make stuff for myself. I have little choice when, as others have already pointed out, when you're on a dead realm it's not always a case of "just get someone to make it for you or buy it off the AH". If I didn't have my professions team I would certainly not pass the "character audit" on this very web site on ANY of my characters. (That's "characters", not "alts". I don't have any alts. This one is the de facto "main" only because she was my first :)
It can also lessen the personal value of playing and connecting with a character. When you have everything, your personal connection to any one of those things is diluted, and you naturally care a little less about each.
That's a broad generalisation. I certainly don't feel any lesser connection with any of my characters for them having their professions.
Let me also explain why they do have them. I love levelling professions. LOVE IT. Ask my guildies, they'll tell you I'm nuts for profession levelling, the harder the better. I'm disappointed at moves to make levelling professions easy one-stop-shop things, and very happy I levelled all of my profs before that happened (I earned Iron Chef back when you had to have every single recipe IN THE ENTIRE GAME ;)
I love hunting down old recipes and get a thrill when I am, say, running Tempest Keep and a pattern drops that my tailor doesn't have. It's FUN.
So sure, I'm self sufficient (to a point - there's still stuff I need others for). But when it comes to things like, say, the Dancing Steel or Jade Spirit enchants, if I couldn't make those myself, I would be heading into Throne of Thunder LFR unenchanted. 5000 gold or more for a single enchant just isn't a consideration.
Note also that I didn't make my characters to be profession mules. I made them to play the various classes, and because I love levelling. I play
my characters. ALL of them. Not always at the same time, mainly because of the amount of time certain activities in the game need sunk into them. But they all get played. They also happen to make me stuff. I worked hard to make that happen. Why is it seen as a "bad thing"?
Maybe one solution is we could say you can only have two professions per Battle.net account! And really strong arm people into it, but of course that'd be a pretty negative change in taking so much away.
"Pretty" negative? Understatement of the year there. Imagine those people with now-unobtainable crafting recipes who would have to choose which ones to lose, for one thing. And us profession fans would have suddenly had a big chunk of our enjoyment of the game sliced away.
I would like to doubt that you were even half serious, but your post here follows Ghostcrawler saying some weeks ago on Twitter that people having profession alts was "not okay". There seems to be internal rumblings on this topic and it worries me.
I wonder if the person who added the "Master of All" achievement is feeling worried too ;)