Two things. First this.
I hear this trotted out now and again and I have to wonder who is equating it with masculinity and maleness? I ask because I just ran through my mental dating data bank and well over half of the femmes I've dated have had their own dildo(s) and probably about half had their own harness.
Maybe we hang out in different crowds? Because I see it and I'm not crazy. Well...
Second. Really? Even for folks who very intimately associate with their cock, dick, etc... it's a necessity? Cause, last time I checked a cock wasn't even a necessity for a bio-male:
See Eunuch.
While I am aware of the Eunuchs (mostly in China and India) I kind of question your comparison of necessity. It's not like Eunuchs live a life of your every day bio-male.
A necessity is that which without, would significantly hamper our ability to make it through our lives, our day to day, as it were. A cock doesn't really seem to fall into this. You may say "but I can't have sex with out..." to which I will say that people the world over take vows of chastity and/or live a celibate life. Sex, despite what we all might like to think, is not a necessity to live. (But ugh, can you imagine a life without it?)
Respectfully, I might disagree with you here. I am not transgender, but from my understanding when one is born into the wrong body and something is missing? Replacing it very well my be a necessity. Not necessarily for sexual reasons, but I don't think we're going to tell an amputee to skip the artificial limb because it's not necessary, are we?
Now, feeling that a cock or anything else is significant to your life and enhances or supplements it in a way that means you put a priority on it... that's still a want, but it's something that you prioritize because you feel it's significant to the way in which you live.
See above.
For me those WANTS which I prioritize include a computer and Internet access. I might even go as far as to say they are a necessity considering that this is how I make my living. However, I could make a living in another way which did not include these items. Of course my standard of living would change dramatically but that's another thread.
What about cell phones?
Finally (oops, guess it wasn't just two things after all, was it?) - years ago I dated a woman who'd lived for a time in Africa doing peace corp work. At the time I had a real shoe thing. I bought shoes ALL THE TIME. I probably had going on 40 pair or so. She had three pair. A pair of sneakers, a pair of Chaco sandals and a pair of boots. It really bothered her that I had so many shoes. She asked why and I said "well, you need shoes". To which she answered... "Do you?. There are countless people the world over who not only don't have shoes and they get along just fine. And the shoes that we consider a necessity are really just luxury. We need something to protect our feet, sure - but could we not just strap some rubber to our feet and call it good?"
Needless to say, that gave me much to think about. I live an extremely comfortable life. I want for very little. But the best part about that is that it's not because I have every toy under the sun, it's because I do not desire every toy under the sun.