Generally speaking - In the last three or four years, I have not seen much "quilting" type fabric at the yard sales I've been at.
Occasionally, there is a bonanza - but not very often. The fabric I have seen - which has not been often - has usually been "non-quilting" types of fabrics.
As far as garments, I have not seen that many 100% woven cotton shirts, either.
When looking at garments at yard sales or thrift shops, read the tags carefully. I bought some that I thought were cotton - but are a blend. Still nice shirts - but they were a cotton-poly blend.
Sewing machines (good, bad, and indifferent) have been few and far between, also.