Shocks are provided on some trailer brands/models and not on others, primarily for cost reasons. The better models still have them, whether newer or older than 2010. I'm reading your message to mean that Cardinal trailers haven't provided shocks since 2010. Shame on them - that's a definite step backwards, cheapening the product in a way that many buyers won't notice until after the sale.
I would certainly replace worn shocks - doing without them will bounce the trailer contents around much more.