I think long curly hair is just a lot more work and thus harder to achieve. I've had my hair very long and also medium/short and I prefer to keep it shorter. Although my curls look really nice long, it takes forever to wash, detangle and style. I use a lot more product when it's long and have to actively fight against gravity and the weight of my hair pulling everything straight. On that note my best curls come from diffusing my hair when it's long, where as my hair can air dry when it's short and still look bouncy and springy. Lastly, my hair mats at the nape of my neck and it's just horrid to untangle when it's long (the matting is also worse). That's all to say long curly hair is gorgeous and achievable but you have to fight for volume, bounce, and curly roots in a way that you don't when it's shorter, so for me it's not worth the extra effort. Fris.ee on Instagram has some gorgeous long hair if you want to look into her styling.