See this mog? This mog makes me feel sexy. What is it? It’s the Lovely Black Dress.
WHY CAN I ONLY USE THIS DURING ‘LOVE IS IN THE AIR’?
Why can I not transmog this OUTSIDE OF THE HOLIDAY? Why can I not choose what makes ME feel sexy year-round? Why does MY choice in what makes ME FEEL GOOD have to be limited by anyone else?
Stop limiting our choices to arbitrary timelines and let me wear what I want to wear so I can feel good about it!
Hello there. I see you posted a complaint of the transmog system. I just wanted to let you know the developers hear and sympathize with your constructive criticism. I’m sure they are working hard to make improvements on the transmog system so you can enjoy your playtime in Azeroth. Thank you and have a nice day! 
It’s strange that they haven’t lifted these restrictions yet.
I can’t imagine that they actually think there’s a reason to make them seasonal only. It must be an oversight or something.
Careful, you’ll get turned into a bowl of fruit!
ROFL quote of the day, folks.
I thought tmogs only applied to gear that was green or better.
Made you laugh, my job is done. 
Correct. White and grey items don’t transmog (though there are many that have green or higher version, possibly recolors).
The dresses haven’t been white or common quality in several years.
So it sounds like, if Blizz was so inclined, they could just make these dresses greens and solve the OP’s issue.
Recently they’ve been making items like this “Use” items that get included as a permanent transmog (and then you lose the item entirely).
They haven’t gotten to all of the holiday stuff (maybe they will or maybe they won’t).
Edit: those items they added “use” to still work by armor type. So if you are plate you won’t be able to use a cloth dress, like this one.
She already has two melons from what I can see. 
Edamann, is that you?
They already are. I linked the original white version but they’re transmoggable as greens and they can ONLY be transmogged during the holiday!
I prefer peaches, but melons aren’t bad either.
/WAGGLE
Would be sexier if you were not standing outside a mud hut and you were a night elf.
I would imagine this is a conscious design choice. The idea of specific holiday gear makes you look forward to doing something different during that timeframe and adds a lot of flavor to the world. I would not expect to see any changes.
Lol. Now you remind me of Sharm’s Tanking in a Dress song.
Conscious design decision by who? The ones who wanted to disempower women and were finally shown the door?
Equip it manually. The gear exists.
I don’t personally think they should be lifted. A lot of Holiday gear is very blatantly tied to the holiday aesthetically, and since the holidays are largely tied directly to real world holidays, I don’t really want to see people dressed for holidays 24/7.
Some cases are worse than others.
The Santa Outfits, for example, are way too blatant and I don’t want to see that 24/7. Same applies to the Pumpkin helmets and such for Hallow’s End. Noblegarden Bunny Ears. That kind of thing. It’s all too blatantly IRL Holiday stuff.
But there are case-by-case Holiday examples that are… less obnoxious IMO.
The Brewfest Outfits fit in mostly okay with WoW’s aesthetic, IMO. But that’s ignoring the dumb pretzel hats. So should specifically the hat be disallowed? Or the whole set for consistency? Or All Holiday transmog for even broader consistency even though the Midsummer Fire Festival Robe is 1000% more in-line with WoW’s look than a Santa Outfit?
That’s where I’m at with this stuff.
Some stuff seems fine.
Other stuff seems obnoxious.
But there’s not a clear place to draw a line other than “Allow all of it” or “Allow none of it”.
So given that, as I said, the gear still exists and can be equipped normally, I guess I learn toward “none of it” if we’re not willing to do a more subjective case-by-case thing.
… and before anyone says it. Yeah, I dislike some things that can currently be transmogged too. Running around in combat with a Rolling Pin Main Hand and Raw Fish Offhand with an Apron Tabard, or god forbid, the freaking Yeti Costume from Blizzcon… are not things I like seeing. But I don’t see them as reasons to make it worse.