Awk has a nifty built-in variable users can overwrite called OFS. OFS stands for output field separator.

Pretend I have a file which has 5 columns separated by single spaces, each of which I would like to print via AWK in tab-separated format.

Life without OFS:

cat file.txt | awk -F" " '{print $1"\t"$2"\t"$3"\t"$4"\t"$5}'

Sticking a "\t" between each variable proves to be very annoying when scaled up.

Life with OFS:

cat file.txt | awk -F" " 'BEGIN{OFS="\t";}{print $1,$2,$3,$4,$5}'

This seems a tad more reasonable. There is certainly less typing involved. The example I provided may not be the best use case, but it definitely shows the capability of OFS and where it can be useful.