Do you want to make baby socks that stay on? Do you want the benefits of ribbing without the appearance of it? Do you want ribbing that doesn't stretch out of shape?
Years ago, I followed a vintage glove pattern. In it, you made the ribbed cuff, then worked one round of eyelets (*k2tog, yo* all the way around), and then worked the same number of rounds as the ribbing in stockinette. When finishing the glove, you folded the ribbing inside the stockinette along the eyelet round, and tacked down the ribbing so it couldn't unfold.
The purpose of all that hullabaloo in that pattern was to hide the ribbing while creating an attractive scalloped edge on the cuffs of the gloves, which is what *k2tog, yo* around looks like when folded in half. However, I've found since then, that the technique has practical purposes that more than justify the effort. Containing ribbing with your pattern stitch, whether it's stockinette or not, limits how far it can stretch, thereby preventing the ribbing from stretching out of shape. I especially like using this technique for baby socks, because it really helps the socks stay on!
As for the eyelet round, the yarn overs make that round act like a perforation. Your work wants to fold along that line, but you might not want the scalloped edge it creates on the finished product or just not want to bother with the effort. In that case, working a purl round also makes an effective fold line.
If you want to create a folded cuff in a pattern, leave a long tail when you cast on, work your ribbing as desired, work one round/right-side row of purl or *k2tog, yo*, and then work in stockinette or your chosen pattern stitch for the same number of rounds/rows as you worked the ribbing. At the end of your project, fold the ribbing into the cuff and use the long cast on tail to tack the ribbing in place.
This might not be a technique you want to use all the time, but it's a handy one to have in your repertoire.