Echo changes my tabs to spaces
Try:
cat inputfile.txt | while read line; do echo "$line"; doneinstead.
In other words, it's not read replacing the tabs, it's echo.
See the following transcript (using <<tab>> where the tabs are):
pax$ echo 'hello<<tab>>there' | while read line ; do echo $line ; donehello therepax$ echo 'hello<<tab>>there' | while read line ; do echo "$line" ; donehello<<tab>>there