We were so glad to see someone addressing this enduring mystery.
The fact of the matter is, the industry standard for measurements in the 1950s was a 10" difference between the bust and waist. That means if you find a dress with a 36" bust measurement, 9 times out of 10, that dress will have a waist that measures 26". If you don't have a waist that is 10" smaller than your bust (and believe me, most of us modern women don't), that explains why you're having a difficult time in your search.
But...why? Why were they so much smaller? After all, most of our grandmothers were and are approximately human in scale. Sure, the average may have been more petite, but not so much as to explain the number of weensy garments out there. The answer is foundation garments, serious foundation garments. Think girdles, merry-widows, waist-cinchers, all of which were to Spanx what the Naga Viper pepper is to a jalapeno and did not exist in the same stratosphere as the concept of "comfort." Seriously, when you try on an authentic vintage girdle you require a whole new respect both for prior generations and the cast of Mad Men.
Did women actually train their waists to be smaller? I doubt most of them gave themselves the chance to find out, at least through the mid-'60. (A phenomenon I've also observed with shoes; could everyone have been a size 6? To judge by vintage offerings, you'd think so. And yet, by the time she'd hit old age, my formerly-5 1/2 grandma was in size 8s. Had her feet spread, or was she simply not cramming them for the first time in half a century? The world may never know.)
Let's face it, even when they fit, clothes of the 50's are less than comfy: skirts make sitting and walking a challenge; tops are boxier than we're used to and without bullet-front bras and crinolines, a lot of the dresses look anachronistic — or, if authentically underpinned, somewhat costumey. Which isn't to say these items can't be fantastic wardrobe additions, whether you're pulling a total Von Teese-style suffer-for-beauty or just throwing on a cotton sundress on a hot day. There is an allure, not merely to the Audrey-and-Grace aesthetic of the period, but of channeling a time when people were just so totally put-together.
So, what to do? Especially if you feel like eating a meal while dressed? Couture Allure has a lot of great suggestions, that range from buying separates to sewing from vintage patterns. To this I'd add: if all else fails, just take inspiration from styles of the past; often modern reworkings can be friendlier to budget, body and even the contemporary eye. That said, if you ever get the chance to do the full Eisenhower-era suit-up, I think you'll agree with me that there are few reliefs greater than undressing and breathing again, despite the alarming marks foundation garments might leave on your poor trunk. After all, sometimes part of the interest of visiting the past is knowing you can take it off at the end of the day.
Why Can't I Find 50's Fashions That Will Fit Me? [Couture Allure]