i think that may be a (local store) decision---my joannes still carry all of those products- on the bolt- i just bought 6 yds of heat n bond lite a few days ago.
check joanne's on line if your local store doesn't have what you need.
my lqs also carries heat N bond lite, steam a seam lite and a few others....they may have (discontinued) wonder-under---i bought a whole bolt of it from joannes a couple years ago and had to return it---it did not (work) it was impossible to remove the paper & when i called customer service they told me to just return it- that they thought they had a 'bad-batch'...it may be that it is no longer available---i haven't tried finding it since then= i stick with the heat & bond or steam a seam or pellon products.