You can certainly get away with rigid tiedown chains or straps.
Lots of people get away with lots of things. Often for their entire lives.
Doesn't mean it's the right way, or even the wrong way. It's just a way.
However, when you have the chance to add features, and cover certain situations the first time around, for a few dollars more, why would you NOT?
In most cases new TCers don't have anything at all to secure their TCs. Since they have to buy turnbuckles anyway, it only makes sense to buy the purpose-built spring-loaded turnbuckles!
What doesn't make sense is buying rigid turnbuckles, only to find out that they're not going to work for you, and you have to spend even more money on a SECOND set of spring-loaded turnbuckles.
Hopefully if I say the same thing over and over, in different ways, people will get the message:
Don't buy twice when you can spend a little extra the first time around and have all your bases covered.
