When did slimline cards become popular?

When die, envelope, etc. manufacturers needed to sell more stuff? </snark>

I don't particularly like them, either... I'm not a fan of 'vertical' formats, I guess. I don't even like vertical / portrait oriented photography, and I scrap 12x12, so the slimline cards (they fit inside a business sized envelope, right?) just aren't a 'natural' sort of size/shape for me to work on.

eta:  and I'm cynical enough to also agree that the main reason for their popularity is to sell more / different sized dies, stamps, etc.  

In the scrapbook I made as a teen (old style, scotch tape, etc) I have many cards that would be considered slimline. What is old is always new again!

Mainstream popular, this year. In terms of selling all the dies. And in terms of me buying a couple of the dies

They've been on my radar for about a year, but this crafter Nicky Meek (https://www.instagram.com/nickynoocards/) has been sharing them pretty regularly for about 2 years. I think some of her cards popped up in my feed about a year ago, but this is one of the earliest I found on her grid (Oct 2018). She does really cool things with them, both landscape and portrait style.

http://instagr.am/p/BpE8ULCF-mf

They sometimes solve a specific problem for me - like using larger die cuts to create scenes. I tried every possible way to make these stockings work on an A2 card but they just wouldn't.
Xmas card by jo.blackford, on Flickr

These stamps were a bit too big to do a 3 photo strip card like I planned, but they looked pretty cool with a 4th on a slimline card.
January cards by jo.blackford, on Flickr

I did a slimline Xmas card for family last year using a cut file. It was just something different.
Friends and family Christmas cards by jo.blackford, on Flickr

I’m old. Like old, old. LOL. Over the years (um, I guessing up to about 8-10 years ago) I’ve chosen boxed Hallmark and Gibson “slimline” cards for our Christmas cards. I think they were pretty popular in the 80’s and early 90’s. We used to have the cards personalized at the card stores (Merry Christmas from the ......). That was the only downside of buying those cards....it couldn’t be done in-house because of the shape of the card and had to be sent out and it cost a pretty penny. 

I think it might be fun to make a few, but I’m not going to invest in any dies anytime soon. 

I've been making them for years, so they aren't new to me. I think the manufacturers gave a heads-up to the "influencers," who started to make more of these types of cards to start a frenzy over them ahead of time. I have no plans to buy anything special, since I can use what I already have.

I had no idea they were a trend. I think I prefer regular card sizes (A2, A7) proportionally, but I can see the appeal. When I was out of regular envelopes, I realized I had a box of “security” envelopes that I used to mail my rent check in, so I cut a bunch of card bases to fit them. It’s a much smaller size, so that was actually pretty fun to work with for a change.

I’m sitting on the bench with you.

Thank you, although all the credit goes to Lori Whitlock
I just picked the shades of blue. 

Still... your cards are the amazing work I was talking about.

Same!

I've been making them for years. Maybe 10 years or so. I don't have any pictures anymore. I started because I had a TON of business size envelopes I wanted to get rid of. Imagine my surprise just lately to hear they are a "thing"now. I don't have any dies and won't purchase any but I may look on the Silhouette store to see if they have anything there.