i don't always use only conditioner leave in as a styler, but i frequently do, and this winter have almost exclusively done so, using ss dd as my leave in. in extremely low dewpoints, i do use a sealant on top when i sotc.
if you think about it, curly hair needs lots of moisture, and when it has the right amount, it curls pretty much to it's potential.
i find that my hair is softer, much less likely to frizz for some strange reason.
i do use stylers from time to time, one of which i use as a styler is beauticurls leave in conditioner! that really pumps up my curls.