It is mostly used in the garment industry because it uses a looper instead of a bobbin. Don’t have to change spools as often.
For home use, it is a stretch stitch, may have more stretch then you get with the stretch stitch on a home sewing machine. Varies with coverstitch machines.
Chainstitching can be done at higher speeds on both domestic and industrial machines.
You can use heavy threads in the needle, and other types in the looper (ribbon, yarn, bulky nylon, fluffy thread, ect)
Sergers/coverstitch machines are usually stronger than a home sewing machine, so if you need to do outdoor fabric, heavy canvas, heavy jeans denim ect.
Some use it the looper side as a decorative stitch.
For machine basting as well, you can remove the chainstitch easily by just pulling the looper thread from the underside, from the seam end, not form seam start..
The most common item to find chainstitchs on jeans, in the leg hem and waistbands. You can find this also on the outseam and inseam of pants, side seams of shirts, hems on knits and tee shirts.
If your sewing machine is broken and in the shop and you need to get a project done, you can use this stitch just like a regular straight stitch and get a project done.
Biggest disadvantage is tends to unravel at the start and mostly at the end of stitch. But this can be greatly minimised by learning a few methods and techniques. Video here, https://youtu.be/jPEtNZX0idc
Some advice, never yank or hard tug your fabric after you chainstitch or serge, I know several if not most instructional videos they do that. There is no reason for that, and it is a good way to bend any of the mechanisms on or under the needle plate. Not to mention may bend a needle also.
Owning both the serger Singer Finishing Touch™ 14SH654, serger/coverstitch combo Singer Professional 5 14T968DC, I am going to try to become super proficient and skilled with these two machines. I want to be the goto person for using both of them.
I have made a playlist of some videos of chainstiching, https://bitlylink.com/b053a
Sources for this article
Difference between chain and lock stitch: https://bitlylink.com/58Bcn