As example:

echo ==> list current working directory
echo "" ==> prints a ''
var=''; echo "$var" ==> prints a ''
echo '' >file; cat file ==> prints a ''
echo '' >file; a=cat file; echo "$a" ==> either print a '*'

but

echo "" >b; for i in cat b; do echo "$i"; done ==> list current working directory instead of print a ''

same behavior showing other wildcards like '?'

Strangely the "while read i; do echo "$i"; done < <textfile_with_wildcard_in>
don't show any result.
While a:
while read i; do echo "$i"; done <<<cat <textfile_with_wildcard_in>
has the exact desired result, of printing the wildcard