I’m not a frum woman, but would like to offer several posibilities, if I may.
. Its easier to shlep around a baby in a carriage.
. Their pocketbooks are filled with enough junk and are already heavy enough. The extra weight just isn’t possible.
. When slings are sold in stores named “Le Snobbe Baby Gear”, or can be advertised as “100% pure Italian fabric” or have a Dolce and Gabana monogram on them, everyone will wear one. Even those with no kids to shlep around will tie one on and put in a watermelon.
. Our heilige bubbes didn’t do it in “der alte heim”.
. Slings sounds like a medical device and they want to avoid ayin hara. Call it a sash and people will buy it.
. The tznius police don’t like it. I’m not sure why, but I’m sure they don’t.