As in not a single thing? No special teddy, first baby shoes, the blanket knitted by granny?
My husband and his three siblings (all in their 30s) have absolutely nothing left from under the age of about 15 (when they got weekend jobs and were able to buy their own stuff) not a sausage
There is no physical record of their childhood left, apart from a few packets of photos- I've only ever seen about half a dozen photographs of my husband as a child/teen
Pils have nothing stashed in their attic either (I know because I helped them move house) DH says they never did.
They have plenty of ornaments and knickknacks on display, so it isn't minimalism, they were comfortably off and lived in a big house with loads of storage, including a massive attic, so it wasn't a space issue, so I can only assume they aren't sentimental that way (though they have loads of pictures and items that belonged to their own parents/holiday souvenirs on display)
It only really struck me as unusual when I was boxing away some of toddler DD's baby things - I've kept a few outfits, a silver baby bracelet, her baby book and a special blanket, which seems about what most of my friends and family seem to keep (apart from one friend who kept every single thing in the garage for years!)
AIBU to think it's a bit strange? Friends of mine have Lego sets that are being played with after spending a few decades in the grandparents attic, and I've also kept some doll's house furniture for DD when she's older - I don't like clutter but it's nice to pass on one or two special items and keep a few bits for memories.